fix CPP_NAME for independently built qfcc

tools/qfcc/configure.in

@@ -23,9 +23,23 @@ AC_PROG_CPP
 AC_PROG_YACC
 AM_PROG_LEX
 
-CPP_NAME=$ac_cv_prog_CPP
-AC_DEFINE_UNQUOTED(CPP_NAME, "$CPP_NAME",
-				   [Define this to the command line for the C preprocessor])
+AC_ARG_WITH(cpp,
+[  --with-cpp=CPP          how qfcc should invoke cpp],
+	cpp_name="$withval", cpp_name=auto
+)
+if test "x$cpp_name" != xauto; then
+	CPP_NAME="$cpp_name"
+else
+	CPP_NAME="cpp %d -o %o %i"
+	case "$target_os" in
+		*bsd*)
+			touch conftest.c
+			CPP_NAME="`(f=\`$CC -v -E -Dfoo conftest.c -o conftest.i 2>&1 | grep -e -Dfoo\`; set $f; echo "$1")` %d %i %o"
+			rm -f conftest.[ci]
+			;;
+	esac
+fi
+AC_DEFINE_UNQUOTED(CPP_NAME, "$CPP_NAME", [Define this to the command line for the C preprocessor])
 
 dnl We want warnings, lots of warnings...
 if test "x$GCC" = xyes; then