FS-6406: --resolve add a way to specify build compiler for cross compile

Makefile.am

@@ -410,7 +410,7 @@ $(OUR_MODULES): $(switch_builddir)/modules.conf libfreeswitch.la
 	test -z "$$fail"
 
 build/print_git_revision: build/print_git_revision.c
-	$(CC) -o $@ $<
+	$(CC_FOR_BUILD) -o $@ $<
 
 src/switch_version.lo: src/include/switch_version.h
 

configure.ac

@@ -218,6 +218,14 @@ AC_PROG_LIBTOOL
 #Check for compiler vendor
 AX_COMPILER_VENDOR
 
+# Set CC_FOR_BUILD
+if test "x${cross_compiling}" = "xyes"; then
+    CC_FOR_BUILD=${CC_FOR_BUILD-gcc}
+else
+    CC_FOR_BUILD='$(CC)'
+fi
+AC_SUBST(CC_FOR_BUILD)
+
 #  Optimize
 AC_ARG_ENABLE(optimization,
 [AC_HELP_STRING([--enable-optimization],[Set if you want us to add max optimising compiler flags])],[enable_optimizer="$enableval"],[enable_optimizer="no"])