- Fix CC / CXX environment variable detection n build-mg.sh

- gitignore build-mg.sh's build/ at the new location

.gitignore

@@ -56,7 +56,7 @@ $RECYCLE.BIN/
 *.blend
 *.blend1
 # Linux_build
-/build/
+/mk/linux/build/
 /google-breakpad
 /mk/linux/megaglest.6
 # Windows_build

mk/linux/build-mg.sh

@@ -173,7 +173,7 @@ if [ $CLANG_FORCED = 1 ]; then
 #exit 1;
 # If both the $CC and $CXX environment variable point to something containing
 # "clang", use whatever these environment variables point to.
-elif [ "`echo $CC | grep -Fq 'clang'`" = 'clang' -a "`echo $CXX | grep -Fq 'clang'`" = 'clang' ]; then
+elif [ "`echo $CC | grep -oF 'clang'`" = 'clang' -a "`echo $CXX | grep -oF 'clang'`" = 'clang' ]; then
 	if [ `echo $CC | grep -Fq '/'` = '/' ]; then
 		CLANG_CC=$CC
 	else