fix gcc detection


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@300 a5019735-40e9-0310-863c-91ae7b9d1cf9
diff --git a/configure.in b/configure.in
index d04bad2..3e0096e 100644
--- a/configure.in
+++ b/configure.in
@@ -37,7 +37,7 @@
 # We don't want gcc 2.7
 AC_MSG_CHECKING([for a supported version of gcc])
 
-gcc_version=`${CC} --version`
+gcc_version=`${CC} --version | head -n 1`
 
 case "${gcc_version}" in
      gcc-2.7.*)