Honor CC environment variable if set.
https://groups.google.com/g/lp_solve/c/851Xedgw4yg
--- bfp/bfp_LUSOL/ccc.orig	2009-01-25 03:03:22.000000000 -0600
+++ bfp/bfp_LUSOL/ccc	2021-01-08 03:03:09.000000000 -0600
@@ -1,7 +1,7 @@
 :
 src='../../shared/commonlib.c ../../colamd/colamd.c lp_LUSOL.c ../../lp_utils.c ../../shared/myblas.c LUSOL/lusol.c'
 
-c=cc
+c=${CC:-cc}
 
 #determine platform (32/64 bit)
 >/tmp/platform.c
--- bfp/bfp_LUSOL/ccc.osx.orig	2009-08-09 03:46:22.000000000 -0500
+++ bfp/bfp_LUSOL/ccc.osx	2021-01-08 03:03:09.000000000 -0600
@@ -1,7 +1,7 @@
 :
 src='../../shared/commonlib.c ../../colamd/colamd.c lp_LUSOL.c ../../lp_utils.c ../../shared/myblas.c LUSOL/lusol.c'
 
-c=cc
+c=${CC:-cc}
 
 #determine platform (32/64 bit)
 >/tmp/platform.c
--- demo/ccc.orig	2005-06-23 13:52:04.000000000 -0500
+++ demo/ccc	2021-01-08 03:03:09.000000000 -0600
@@ -1,5 +1,5 @@
 src='../lp_MDO.c ../shared/commonlib.c ../colamd/colamd.c ../shared/mmio.c ../shared/myblas.c ../ini.c ../lp_rlp.c ../lp_crash.c ../bfp/bfp_LUSOL/lp_LUSOL.c ../bfp/bfp_LUSOL/LUSOL/lusol.c ../lp_Hash.c ../lp_lib.c ../lp_wlp.c ../lp_matrix.c ../lp_mipbb.c ../lp_MPS.c ../lp_params.c ../lp_presolve.c ../lp_price.c ../lp_pricePSE.c ../lp_report.c ../lp_scale.c ../lp_simplex.c ../lp_SOS.c ../lp_utils.c ../yacc_read.c'
-c=cc
+c=${CC:-cc}
 
 math=-lm
 
--- demo/ccc.osx.orig	2005-06-11 14:27:44.000000000 -0500
+++ demo/ccc.osx	2021-01-08 03:03:09.000000000 -0600
@@ -1,5 +1,5 @@
 src='../bfp/lp_MDO.c ../commonlib.c ../myblas.c ../colamd/colamd.c ../ini.c ../fortify.c ../lp_rlp.c ../lp_crash.c ../bfp/bfp_etaPFI/lp_etaPFI.c ../lp_Hash.c ../lp_lib.c ../lp_wlp.c ../lp_matrix.c ../lp_mipbb.c ../lp_MPS.c ../lp_params.c ../lp_presolve.c ../lp_price.c ../lp_pricePSE.c ../lp_report.c ../lp_scale.c ../lp_simplex.c demo.c ../lp_SOS.c ../lp_utils.c ../yacc_read.c'
-c=cc
+c=${CC:-cc}
 
 math=-lm
 
--- lp_solve/ccc.orig	2020-11-23 10:27:17.000000000 -0600
+++ lp_solve/ccc	2021-01-08 03:03:09.000000000 -0600
@@ -1,6 +1,6 @@
 :
 src='../lp_MDO.c ../shared/commonlib.c ../colamd/colamd.c ../shared/mmio.c ../shared/myblas.c ../ini.c ../fortify.c ../lp_rlp.c ../lp_crash.c ../bfp/bfp_LUSOL/lp_LUSOL.c ../bfp/bfp_LUSOL/LUSOL/lusol.c ../lp_Hash.c ../lp_lib.c ../lp_wlp.c ../lp_matrix.c ../lp_mipbb.c ../lp_MPS.c ../lp_params.c ../lp_presolve.c ../lp_price.c ../lp_pricePSE.c ../lp_report.c ../lp_scale.c ../lp_simplex.c lp_solve.c ../lp_SOS.c ../lp_utils.c ../yacc_read.c'
-c=cc
+c=${CC:-cc}
 
 MYTMP=`mktemp -d "${TMPDIR:-/tmp}"/lp_solve_XXXXXX`
 
--- lp_solve/ccc.osx.orig	2020-11-23 10:24:43.000000000 -0600
+++ lp_solve/ccc.osx	2021-01-08 03:03:09.000000000 -0600
@@ -1,6 +1,6 @@
 :
 src='../lp_MDO.c ../shared/commonlib.c ../colamd/colamd.c ../shared/mmio.c ../shared/myblas.c ../ini.c ../fortify.c ../lp_rlp.c ../lp_crash.c ../bfp/bfp_LUSOL/lp_LUSOL.c ../bfp/bfp_LUSOL/LUSOL/lusol.c ../lp_Hash.c ../lp_lib.c ../lp_wlp.c ../lp_matrix.c ../lp_mipbb.c ../lp_MPS.c ../lp_params.c ../lp_presolve.c ../lp_price.c ../lp_pricePSE.c ../lp_report.c ../lp_scale.c ../lp_simplex.c lp_solve.c ../lp_SOS.c ../lp_utils.c ../yacc_read.c'
-c=cc
+c=${CC:-cc}
 
 MYTMP=`mktemp -d "${TMPDIR:-/tmp}"/lp_solve_XXXXXX`
 
--- lpsolve55/ccc.orig	2020-11-23 10:27:40.000000000 -0600
+++ lpsolve55/ccc	2021-01-08 03:03:09.000000000 -0600
@@ -1,6 +1,6 @@
 :
 src='../lp_MDO.c ../shared/commonlib.c ../shared/mmio.c ../shared/myblas.c ../ini.c ../fortify.c ../colamd/colamd.c ../lp_rlp.c ../lp_crash.c ../bfp/bfp_LUSOL/lp_LUSOL.c ../bfp/bfp_LUSOL/LUSOL/lusol.c ../lp_Hash.c ../lp_lib.c ../lp_wlp.c ../lp_matrix.c ../lp_mipbb.c ../lp_MPS.c ../lp_params.c ../lp_presolve.c ../lp_price.c ../lp_pricePSE.c ../lp_report.c ../lp_scale.c ../lp_simplex.c ../lp_SOS.c ../lp_utils.c ../yacc_read.c'
-c=cc
+c=${CC:-cc}
 
 MYTMP=`mktemp -d "${TMPDIR:-/tmp}"/lp_solve_XXXXXX`
 
--- lpsolve55/ccc.aix.orig	2016-12-10 03:04:23.000000000 -0600
+++ lpsolve55/ccc.aix	2021-01-08 03:03:09.000000000 -0600
@@ -4,7 +4,7 @@
 type xlc >/dev/null 2>&1
 if [ $? = 0 ]
 then c=xlc
-else c=cc
+else c=${CC:-cc}
 fi
 
 #determine platform (32/64 bit)
--- lpsolve55/ccc.hp-ux.orig	2016-12-10 03:04:29.000000000 -0600
+++ lpsolve55/ccc.hp-ux	2021-01-08 03:03:09.000000000 -0600
@@ -1,6 +1,6 @@
 :
 src='../lp_MDO.c ../shared/commonlib.c ../shared/mmio.c ../shared/myblas.c ../ini.c ../fortify.c ../colamd/colamd.c ../lp_rlp.c ../lp_crash.c ../bfp/bfp_LUSOL/lp_LUSOL.c ../bfp/bfp_LUSOL/LUSOL/lusol.c ../lp_Hash.c ../lp_lib.c ../lp_wlp.c ../lp_matrix.c ../lp_mipbb.c ../lp_MPS.c ../lp_params.c ../lp_presolve.c ../lp_price.c ../lp_pricePSE.c ../lp_report.c ../lp_scale.c ../lp_simplex.c ../lp_SOS.c ../lp_utils.c ../yacc_read.c'
-c=cc
+c=${CC:-cc}
 
 #determine platform (32/64 bit)
 >/tmp/platform.c
--- lpsolve55/ccc.osx.orig	2020-11-23 10:25:41.000000000 -0600
+++ lpsolve55/ccc.osx	2021-01-08 03:03:09.000000000 -0600
@@ -1,6 +1,6 @@
 :
 src='../lp_MDO.c ../shared/commonlib.c ../shared/mmio.c ../shared/myblas.c ../ini.c ../fortify.c ../colamd/colamd.c ../lp_rlp.c ../lp_crash.c ../bfp/bfp_LUSOL/lp_LUSOL.c ../bfp/bfp_LUSOL/LUSOL/lusol.c ../lp_Hash.c ../lp_lib.c ../lp_wlp.c ../lp_matrix.c ../lp_mipbb.c ../lp_MPS.c ../lp_params.c ../lp_presolve.c ../lp_price.c ../lp_pricePSE.c ../lp_report.c ../lp_scale.c ../lp_simplex.c ../lp_SOS.c ../lp_utils.c ../yacc_read.c'
-c=cc
+c=${CC:-cc}
 
 MYTMP=`mktemp -d "${TMPDIR:-/tmp}"/lp_solve_XXXXXX`
 
--- lpsolve55/ccc.solaris.orig	2016-12-10 03:04:37.000000000 -0600
+++ lpsolve55/ccc.solaris	2021-01-08 03:03:09.000000000 -0600
@@ -1,6 +1,6 @@
 :
 src='../lp_MDO.c ../shared/commonlib.c ../shared/mmio.c ../shared/myblas.c ../ini.c ../fortify.c ../colamd/colamd.c ../lp_rlp.c ../lp_crash.c ../bfp/bfp_LUSOL/lp_LUSOL.c ../bfp/bfp_LUSOL/LUSOL/lusol.c ../lp_Hash.c ../lp_lib.c ../lp_wlp.c ../lp_matrix.c ../lp_mipbb.c ../lp_MPS.c ../lp_params.c ../lp_presolve.c ../lp_price.c ../lp_pricePSE.c ../lp_report.c ../lp_scale.c ../lp_simplex.c ../lp_SOS.c ../lp_utils.c ../yacc_read.c'
-c=cc
+c=${CC:-cc}
 
 #determine platform (32/64 bit)
 >/tmp/platform.c
--- lpsolve55/cccLUSOL.osx.orig	2016-12-10 03:04:57.000000000 -0600
+++ lpsolve55/cccLUSOL.osx	2021-01-08 03:03:09.000000000 -0600
@@ -1,5 +1,5 @@
 src='../lp_MDO.c ../shared/commonlib.c ../shared/mmio.c ../shared/myblas.c ../ini.c ../fortify.c ../colamd/colamd.c ../lp_rlp.c ../lp_crash.c ../bfp/bfp_LUSOL/lp_LUSOL.c ../bfp/bfp_LUSOL/LUSOL/lusol.c ../lp_Hash.c ../lp_lib.c ../lp_wlp.c ../lp_matrix.c ../lp_mipbb.c ../lp_MPS.c ../lp_params.c ../lp_presolve.c ../lp_price.c ../lp_pricePSE.c ../lp_report.c ../lp_scale.c ../lp_simplex.c ../lp_SOS.c ../lp_utils.c ../yacc_read.c ../bfp/bfp_LUSOL/lusol.c'
-c=cc
+c=${CC:-cc}
 
 #determine platform (32/64 bit)
 >/tmp/platform.c