minijail: fix input validation in gen_constants.sh

Add missing whitespace to input validation check in
gen_constants.sh, so that this check actually runs.

While there, reduce the 3-argument version of this
script to 2 arguments by combining the path to the
compiler binary and the arguments to pass to
the compiler into one argument.

BUG=chromium:539662
TEST=minijail builds using emerge.

Change-Id: Ib31688b034d960b6dbb2cb241401ef560f3c517f
diff --git a/gen_constants.sh b/gen_constants.sh
index 8dcbca2..0ad29ba 100755
--- a/gen_constants.sh
+++ b/gen_constants.sh
@@ -11,17 +11,15 @@
 
 set -e
 
-if [ $# -ne 1 ] && [ $# -ne 3]; then
+if [ $# -ne 1 ] && [ $# -ne 2 ]; then
   echo "Usage: $(basename "$0") OUTFILE"
-  echo "Usage: $(basename "$0") CC CFLAGS OUTFILE"
+  echo "Usage: $(basename "$0") CC OUTFILE"
   exit 1
 fi
 
-if [ $# -eq 3 ]; then
+if [ $# -eq 2 ]; then
   CC="$1"
   shift
-  CFLAGS="$1"
-  shift
 fi
 OUTFILE="$1"
 
@@ -45,7 +43,7 @@
 #include "libconstants.h"
 const struct constant_entry constant_table[] = {
 $(echo "$INCLUDES" | \
-  ${CC} ${CFLAGS} -dD - -E | \
+  ${CC} -dD - -E | \
   grep '^#define [A-Z][A-Z0-9_]* ' | \
   grep -v '\(SIGRTMAX\|SIGRTMIN\|SIG_\|NULL\)' | \
   sort | \