eukleides: use $CC instead of hardcoded gcc

pkgs/applications/science/math/eukleides/default.nix

@@ -9,6 +9,9 @@ lib.fix (eukleides: stdenv.mkDerivation rec {
     sha256 = "0s8cyh75hdj89v6kpm3z24i48yzpkr8qf0cwxbs9ijxj1i38ki0q";
   };
 
+  # use $CC instead of hardcoded gcc
+  patches = [ ./use-CC.patch ];
+
   nativeBuildInputs = [ bison flex texinfo makeWrapper ];
 
   buildInputs = [ readline texLive ];
@@ -59,7 +62,7 @@ lib.fix (eukleides: stdenv.mkDerivation rec {
       circles and conics.
     '';
 
-    platforms = lib.platforms.linux;
+    platforms = lib.platforms.unix;
     maintainers = [ lib.maintainers.peti ];
   };
 })

pkgs/applications/science/math/eukleides/use-CC.patch

@@ -0,0 +1,11 @@
+--- a/build/Makefile
++++ b/build/Makefile
+@@ -11,7 +11,7 @@ LEX = flex
+ LFLAGS = -8
+ YACC = bison
+ YFLAGS = -d
+-CC = gcc
++CC ?= gcc
+ IFLAGS = -I$(COMMON_DIR) -I$(MAIN_DIR) -I$(BUILD_DIR) 
+ ifneq ($(strip $(LOCALES)),)
+ MOFLAGS = -DMO_DIR=\"$(MO_DIR)\"