append instead of prepend CFLAGS for the other makefiles

makefile.mingw

@@ -25,7 +25,7 @@ CFLAGS    = -O2 -DUSE_LTM -DLTM_DESC -I../libtommath
 EXTRALIBS = -L../libtommath -ltommath
 
 #Compilation flags
-LTC_CFLAGS  = $(CFLAGS) -Isrc/headers -Itests -DLTC_SOURCE
+LTC_CFLAGS  = -Isrc/headers -Itests -DLTC_SOURCE $(CFLAGS)
 LTC_LDFLAGS = $(LDFLAGS) $(EXTRALIBS)
 VERSION=1.18.0-rc1
 

makefile.msvc

@@ -20,7 +20,7 @@ CFLAGS    = /Ox /DUSE_LTM /DLTM_DESC /I../libtommath
 EXTRALIBS = ../libtommath/tommath.lib
 
 #Compilation flags
-LTC_CFLAGS  = $(CFLAGS) /nologo /Isrc/headers/ /Itests/ /D_CRT_SECURE_NO_WARNINGS /D_CRT_NONSTDC_NO_DEPRECATE /DLTC_SOURCE /W3
+LTC_CFLAGS  = /nologo /Isrc/headers/ /Itests/ /D_CRT_SECURE_NO_WARNINGS /D_CRT_NONSTDC_NO_DEPRECATE /DLTC_SOURCE /W3 $(CFLAGS)
 LTC_LDFLAGS = advapi32.lib $(EXTRALIBS)
 VERSION=1.18.0-rc1
 

makefile.unix

@@ -37,7 +37,7 @@ CFLAGS    = -O2 -DUSE_LTM -DLTM_DESC -I../libtommath
 EXTRALIBS = ../libtommath/libtommath.a
 
 #Compilation flags
-LTC_CFLAGS  = $(CFLAGS) -Isrc/headers -Itests -DLTC_SOURCE
+LTC_CFLAGS  = -Isrc/headers -Itests -DLTC_SOURCE $(CFLAGS)
 LTC_LDFLAGS = $(LDFLAGS) $(EXTRALIBS)
 VERSION=1.18.0-rc1