xcompile: Add parameter to aid in debugging

There was a report that xcompile wasn't finding the compilers correctly,
so to aid in future debugging, this adds a parameter to show what
xcompile is doing as it runs.

Run from the command line:
./util/xcompile/xcompile --debug

Change-Id: I779cb3de7b4e3f62a2ef2a6245c3538be518870c
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/13047
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

util/xcompile/xcompile

@@ -15,6 +15,14 @@
 # GNU General Public License for more details.
 #
 
+# Usage: [--debug] [path to xgcc/bin directory]
+
+# Enable debug output
+if [ "$1" = "--debug" ]; then
+	shift
+	set -x
+fi
+
 TMPFILE=""
 XGCCPATH=$1