ld-version: Fix awk regex compile failure

The ld-version.sh script fails on some versions of awk with the
following error, resulting in build failures for MIPS:

awk: scripts/ld-version.sh: line 4: regular expression compile failed (missing '(')

This is due to the regular expression ".*)", meant to strip off the
beginning of the ld version string up to the close bracket, however
brackets have a meaning in regular expressions, so lets escape it so
that awk doesn't expect a corresponding open bracket.

Fixes: ccbef167 ("Kbuild, lto: add ld-version and ld-ifversion ...")
Reported-by: NGeert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: NJames Hogan <james.hogan@imgtec.com>
Tested-by: NMichael S. Tsirkin <mst@redhat.com>
Acked-by: NMichael S. Tsirkin <mst@redhat.com>
Tested-by: NSudip Mukherjee <sudip.mukherjee@codethink.co.uk>
Cc: Michal Marek <mmarek@suse.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: linux-mips@linux-mips.org
Cc: linux-kbuild@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org # 4.4.x-
Patchwork: https://patchwork.linux-mips.org/patch/12838/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

scripts/ld-version.sh

 #!/usr/bin/awk -f
 # extract linker version number from stdin and turn into single number
 	{
-	gsub(".*)", "");
+	gsub(".*\\)", "");
 	gsub(".*version ", "");
 	gsub("-.*", "");
 	split($1,a, ".");