Merge branch 'gcc-detect-case' into 'master'

I guess GCC isn't always "GCC"

See merge request STJr/SRB2!1057

src/Makefile.cfg

@@ -47,7 +47,7 @@ endif
 
 # Automatically set version flag, but not if one was manually set
 ifeq   (,$(filter GCC%,$(.VARIABLES)))
- ifneq (,$(findstring GCC,$(shell $(CC) --version))) # if it's GCC
+ ifneq (,$(findstring gcc,$(shell $(CC) --version))) # if it's GCC
   version:=$(shell $(CC) -dumpversion)
 
   # Turn version into words of major, minor