scripts/test-reexec: fix several incomplete regexp

Some "=" are missing in the regexp, which leads it match multiple results
if the variables have overrides, for instance:
...
SSTATE_DIR="xxxx"
SSTATE_DIR_qemux86="yyyy"
...

it will match both of them without "=".

(From OE-Core rev: 10cb4331caee4b960a6f9ad20023a4a4b69b684e)

Signed-off-by: Ming Liu <peter.x.liu@external.atlascopco.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/test-reexec

@@ -38,9 +38,9 @@ mkdir -p $LOGS
 function clearsstate {
 	target=$1
 
-	sstate_dir=`bitbake $target -e | grep "^SSTATE_DIR" | cut -d "\"" -f 2`
-	sstate_pkgspec=`bitbake $target -e | grep "^SSTATE_PKGSPEC" | cut -d "\"" -f 2`
-	sstasks=`bitbake $target -e | grep "^SSTATETASKS" | cut -d "\"" -f 2`
+	sstate_dir=`bitbake $target -e | grep "^SSTATE_DIR=" | cut -d "\"" -f 2`
+	sstate_pkgspec=`bitbake $target -e | grep "^SSTATE_PKGSPEC=" | cut -d "\"" -f 2`
+	sstasks=`bitbake $target -e | grep "^SSTATETASKS=" | cut -d "\"" -f 2`
 
 	for sstask in $sstasks
 	do