The native compiler on OpenIndiana is gcc. Modify GNU make to suit.
We don't define GCC_IS_NATIVE since this also modifies the native
lex and yacc defitions and makes the POSIX tests fail.

This patch is taken from OmniOS on May 9th, 2021
diff -wpruN '--exclude=*.orig' a~/src/default.c a/src/default.c
--- a~/src/default.c	1970-01-01 00:00:00
+++ a/src/default.c	1970-01-01 00:00:00
@@ -529,9 +529,9 @@ static const char *default_variables[] =
 # endif /* __MSDOS__ */
     "OBJC", "gcc",
 #else
-    "CC", "cc",
+    "CC", "gcc",
     "CXX", "g++",
-    "OBJC", "cc",
+    "OBJC", "gcc",
 #endif
 
     /* This expands to $(CO) $(COFLAGS) $< $@ if $@ does not exist,