configure.ac, configure:

Fix another reference of CC variable

Author: LocutusOfBorg

configure

@@ -879,7 +879,7 @@ AC_SUBST(CXX)
 preset_cxx="$CXX"
 if test -z "$CXX"
 then
-        case "$CC" in
+        case $(basename "$CC") in
         gcc)    AC_PATH_TOOL(CXX, [g++], [g++], [notfound]) ;;
         cc)     AC_PATH_TOOL(CXX, [c++], [c++], [notfound]) ;;
         clang|*/clang)     AC_PATH_TOOL(CXX, [clang++], [clang++], [notfound]) ;;