classes/populate_sdk_ext: parse metadata on minimal SDK install

Instead of skipping the build system preparation step within the
extensible SDK install process when SDK_EXT_TYPE is "minimal", run
bitbake -p so that the cache is populated ready for the first time
devtool is run.

(From OE-Core rev: 6b38a991a3475fb82889428b94563968c7570473)

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/populate_sdk_ext.bbclass

@@ -374,7 +374,7 @@ sdk_ext_postinst() {
 	# Warn if trying to use external bitbake and the ext SDK together
 	echo "(which bitbake > /dev/null 2>&1 && echo 'WARNING: attempting to use the extensible SDK in an environment set up to run bitbake - this may lead to unexpected results. Please source this script in a new shell session instead.') || true" >> $env_setup_script
 
-	if [ "$prepare_buildsystem" != "no" -a -n "${@SDK_INSTALL_TARGETS.strip()}" ]; then
+	if [ "$prepare_buildsystem" != "no" ]; then
 		printf "Preparing build system...\n"
 		# dash which is /bin/sh on Ubuntu will not preserve the
 		# current working directory when first ran, nor will it set $1 when

meta/files/ext-sdk-prepare.py

@@ -30,10 +30,14 @@ def exec_watch(cmd, **options):
 
 def main():
     if len(sys.argv) < 2:
-        print('Please specify target to prepare with')
-        return 1
+        sdk_targets = []
+    else:
+        sdk_targets = ' '.join(sys.argv[1:]).split()
+    if not sdk_targets:
+        # Just do a parse so the cache is primed
+        ret, _ = exec_watch('bitbake -p')
+        return ret
 
-    sdk_targets = ' '.join(sys.argv[1:]).split()
     print('Preparing SDK for %s...' % ', '.join(sdk_targets))
 
     ret, out = exec_watch('bitbake %s --setscene-only' % ' '.join(sdk_targets))