scripts/runqemu: grep for line beginning with TMPDIR

Currently the grep regexp matches any occurance of
'TMPDIR=' but if you have another variable defined
e.g. OE_BUILD_TMPDIR=xxx then that gets picked up
too.

$ bitbake -e | grep TMPDIR=\"
TMPDIR="/home/kraj/work/angstrom/build/tmp-angstrom_2010_x-eglibc"
OE_BUILD_TMPDIR="/home/kraj/work/angstrom/build/tmp-angstrom_2010_x"

So we become a bit more stringent and look for
line starting with TMPDIR

$ bitbake -e | grep ^TMPDIR=\"
TMPDIR="/home/kraj/work/angstrom/build/tmp-angstrom_2010_x-eglibc"

make sure that it greps
only TMPDIR=xxx occurance and not values of other variables
whose names happens to end with TMPDIR

(From OE-Core rev: 12ddf6c6a7559d97d9b8f84fcc89ed02e30df85d)

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/runqemu

@@ -271,7 +271,7 @@ setup_tmpdir() {
             exit 1; }
 
         # We have bitbake in PATH, get TMPDIR from bitbake
-        TMPDIR=`bitbake -e | grep TMPDIR=\" | cut -d '=' -f2 | cut -d '"' -f2`
+        TMPDIR=`bitbake -e | grep ^TMPDIR=\" | cut -d '=' -f2 | cut -d '"' -f2`
         if [ -z "$TMPDIR" ]; then
             echo "Error: this script needs to be run from your build directory,"
             echo "or you need to explicitly set TMPDIR in your environment"