Remove the -Wno-long-double flag which generates a warning that it is
not recognized.
https://groups.google.com/g/lp_solve/c/DPjEkRwrd9Y
--- bfp/bfp_LUSOL/ccc.osx.orig	2009-08-09 03:46:22.000000000 -0500
+++ bfp/bfp_LUSOL/ccc.osx	2021-01-08 03:34:01.000000000 -0600
@@ -14,7 +14,7 @@
 
 mkdir bin bin/$PLATFORM >/dev/null 2>&1
 
-opts='-idirafter /usr/include/sys -O3 -DINTEGERTIME -Wno-long-double'
+opts='-idirafter /usr/include/sys -O3 -DINTEGERTIME'
 
 $c -s -c $opts -I.. -I../.. -I../../colamd -I../../shared -ILUSOL -I. -DRoleIsExternalInvEngine -DINVERSE_ACTIVE=INVERSE_LUSOL $src
 libtool -static -o libbfp_LUSOL.a `echo $src|sed s/[.]c/.o/g|sed 's/[^ ]*\///g'`
--- configure.ac.orig	2009-01-02 11:15:34.000000000 -0600
+++ configure.ac	2021-01-07 23:27:42.000000000 -0600
@@ -21,7 +21,7 @@
   linux)
     CCSHARED="-fPIC";;
   apple-darwin)
-    DEF=-ldl -idirafter /usr/include/sys -DINTEGERTIME -Wno-long-double
+    DEF=-ldl -idirafter /usr/include/sys -DINTEGERTIME
     ;;
   OpenUNIX*|UnixWare*)
     DEF='-dy -DNOLONGLONG'
--- configure.orig	2021-01-07 23:27:42.000000000 -0600
+++ configure	2021-01-07 23:27:42.000000000 -0600
@@ -1357,7 +1357,7 @@
   linux)
     CCSHARED="-fPIC";;
   apple-darwin)
-    DEF=-ldl -idirafter /usr/include/sys -DINTEGERTIME -Wno-long-double
+    DEF=-ldl -idirafter /usr/include/sys -DINTEGERTIME
     ;;
   OpenUNIX*|UnixWare*)
     DEF='-dy -DNOLONGLONG'
--- demo/ccc.osx.orig	2005-06-11 14:27:44.000000000 -0500
+++ demo/ccc.osx	2021-01-07 23:27:42.000000000 -0600
@@ -9,6 +9,6 @@
 else dl=-ldl
 fi
 
-opts='-idirafter /usr/include/sys -O3 -DINTEGERTIME -Wno-long-double'
+opts='-idirafter /usr/include/sys -O3 -DINTEGERTIME'
 
 $c -I.. -I../bfp -I../bfp/bfp_etaPFI -I../colamd $opts $def -DYY_NEVER_INTERACTIVE -DPARSER_LP $src -o demo $math $dl
--- lp_solve/ccc.osx.orig	2020-11-23 10:24:43.000000000 -0600
+++ lp_solve/ccc.osx	2021-01-07 23:27:42.000000000 -0600
@@ -35,6 +35,6 @@
 def=
 dl=-ldl
 
-opts='-idirafter /usr/include/sys -O3 -DINTEGERTIME -Wno-long-double'
+opts='-idirafter /usr/include/sys -O3 -DINTEGERTIME'
 
 $c -I.. -I../bfp -I../bfp/bfp_LUSOL -I../bfp/bfp_LUSOL/LUSOL -I../colamd -I../shared $opts $def $NOISNAN -DYY_NEVER_INTERACTIVE -DPARSER_LP -DINVERSE_ACTIVE=INVERSE_LUSOL -DRoleIsExternalInvEngine $src -o bin/$PLATFORM/lp_solve $math $dl
--- lpsolve55/ccc.osx.orig	2020-11-23 10:25:41.000000000 -0600
+++ lpsolve55/ccc.osx	2021-01-08 03:21:49.000000000 -0600
@@ -34,7 +34,6 @@
 dl=-ldl
 so=y
 
-#opts='-idirafter /usr/include/sys -O3 -DINTEGERTIME -Wno-long-double'
 opts='-idirafter /usr/include/sys -O3 -DINTEGERTIME'
 
 $c -s -c -I.. -I../shared -I../bfp -I../bfp/bfp_LUSOL -I../bfp/bfp_LUSOL/LUSOL -I../colamd $opts $def $NOISNAN -DYY_NEVER_INTERACTIVE -DPARSER_LP -DINVERSE_ACTIVE=INVERSE_LUSOL -DRoleIsExternalInvEngine $src
--- lpsolve55/cccLUSOL.osx.orig	2016-12-10 03:04:57.000000000 -0600
+++ lpsolve55/cccLUSOL.osx	2021-01-07 23:27:42.000000000 -0600
@@ -30,7 +30,7 @@
 dl=-ldl
 so=y
 
-opts='-idirafter /usr/include/sys -O3 -DINTEGERTIME -Wno-long-double'
+opts='-idirafter /usr/include/sys -O3 -DINTEGERTIME'
 
 $c -s -c -I.. -I../shared -I../bfp -I../bfp/bfp_LUSOL -I../bfp/bfp_LUSOL/LUSOL -I../colamd $opts $def $NOISNAN -DYY_NEVER_INTERACTIVE -DPARSER_LP -DINVERSE_ACTIVE=INVERSE_LUSOL -DRoleIsExternalInvEngine $src
 libtool -static -o bin/$PLATFORM/liblpsolve55.a `echo $src|sed s/[.]c/.o/g|sed 's/[^ ]*\///g'`