[OE-core][PATCH] runqemu: restore support to run without bitbake

[Qi.Chen@windriver.com]

From: Chen Qi <Qi.Chen@windriver.com>

This patch is basically a revert of the following three patches:
- 0c10a78796 scripts/runqemu: raise an error when bitbake was not found
- b931f74442 scripts/runqemu: remove the code block that works around the missing bitbake environment
- 8197be4dd3 runqemu: ensure that bitbake environment is either returned, or an exception is raised

The comment is also changed to reflect the current usage:
"invoked from a running bitbake instance" ->
"invoked from environment with no bitbake (e.g., SDK)"

This code path was deleted by accident based on the reason that nobody
is using it. But in fact, running runqemu from SDK needs this code path.
Such case has been supported for years.

A little more history on this code path:
In 2016/09/09, this code path was introduced[1]. It was introduced
originally to handle running bitbake inside bitbake situation.
In 2026/09/19, running runqemu from SDK is supported using this code
path[2]. This means that this code path was then needed by one more case: SDK.

Supporting running nativesdk-qemu from SDK easily via our script dates back to
more than 18 years ago, as shown by 'git blame' on the nativesdk-qemu-helper recipe[3].

[1] https://git.openembedded.org/openembedded-core/commit/?id=1e8165ea2f19aecdc03ccd102ee44ef0544f0f39
[2] https://git.openembedded.org/openembedded-core/commit/?id=93649edc034f2540ff55dc9b41638797209cfb9c
[3] https://git.openembedded.org/openembedded-core/tree/meta/recipes-devtools/qemu/nativesdk-qemu-helper_1.0.bb

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
---
 scripts/runqemu | 47 ++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 36 insertions(+), 11 deletions(-)

diff --git a/scripts/runqemu b/scripts/runqemu
index 32a3d6296a..7e3d11f653 100755
--- a/scripts/runqemu
+++ b/scripts/runqemu
@@ -1007,12 +1007,34 @@ to your build configuration.
             if not self.bitbake_e:
                 self.load_bitbake_env()
 
-            native_vars = ['STAGING_DIR_NATIVE']
-            for nv in native_vars:
-                s = re.search('^%s="(.*)"' % nv, self.bitbake_e, re.M)
-                if s and s.group(1) != self.get(nv):
-                    logger.info('Overriding conf file setting of %s to %s from Bitbake environment' % (nv, s.group(1)))
-                    self.set(nv, s.group(1))
+            if self.bitbake_e:
+                native_vars = ['STAGING_DIR_NATIVE']
+                for nv in native_vars:
+                    s = re.search('^%s="(.*)"' % nv, self.bitbake_e, re.M)
+                    if s and s.group(1) != self.get(nv):
+                        logger.info('Overriding conf file setting of %s to %s from Bitbake environment' % (nv, s.group(1)))
+                        self.set(nv, s.group(1))
+            else:
+                # when we're invoked from environment with no bitbake (e.g., SDK),
+                # we won't be able to call `bitbake -e`, then try:
+                # - get OE_TMPDIR from environment and guess paths based on it
+                # - get OECORE_NATIVE_SYSROOT from environment (for sdk)
+                tmpdir = self.get('OE_TMPDIR')
+                oecore_native_sysroot = self.get('OECORE_NATIVE_SYSROOT')
+                if tmpdir:
+                    logger.info('Setting STAGING_DIR_NATIVE and STAGING_BINDIR_NATIVE relative to OE_TMPDIR (%s)' % tmpdir)
+                    hostos, _, _, _, machine = os.uname()
+                    buildsys = '%s-%s' % (machine, hostos.lower())
+                    staging_dir_native = '%s/sysroots/%s' % (tmpdir, buildsys)
+                    self.set('STAGING_DIR_NATIVE', staging_dir_native)
+                elif oecore_native_sysroot:
+                    logger.info('Setting STAGING_DIR_NATIVE to OECORE_NATIVE_SYSROOT (%s)' % oecore_native_sysroot)
+                    self.set('STAGING_DIR_NATIVE', oecore_native_sysroot)
+                if self.get('STAGING_DIR_NATIVE'):
+                    # we have to assume that STAGING_BINDIR_NATIVE is at usr/bin
+                    staging_bindir_native = '%s/usr/bin' % self.get('STAGING_DIR_NATIVE')
+                    logger.info('Setting STAGING_BINDIR_NATIVE to %s' % staging_bindir_native)
+                    self.set('STAGING_BINDIR_NATIVE', '%s/usr/bin' % self.get('STAGING_DIR_NATIVE'))
 
     def print_config(self):
         logoutput = ['Continuing with the following parameters:']
@@ -1691,6 +1713,9 @@ to your build configuration.
         self.cleaned = True
 
     def run_bitbake_env(self, mach=None, target=''):
+        bitbake = shutil.which('bitbake')
+        if not bitbake:
+            return
 
         if not mach:
             mach = self.get('MACHINE')
@@ -1707,10 +1732,6 @@ to your build configuration.
         else:
             cmd = 'bitbake -e %s %s' % (multiconfig, target)
 
-        bitbake = shutil.which('bitbake')
-        if not bitbake:
-            raise OEPathError("Bitbake is needed to run '%s', but it is not found in PATH. Please source the bitbake build environment." % cmd.strip())
-
         logger.info('Running %s...' % cmd)
         try:
             return subprocess.check_output(cmd, shell=True).decode('utf-8')
@@ -1722,7 +1743,11 @@ to your build configuration.
                 cmd = 'MACHINE=%s bitbake -e %s %s' % (mach, multiconfig, target)
             else:
                 cmd = 'bitbake -e %s %s' % (multiconfig, target)
-            return subprocess.check_output(cmd, shell=True).decode('utf-8')
+            try:
+                return subprocess.check_output(cmd, shell=True).decode('utf-8')
+            except subprocess.CalledProcessError as err:
+                logger.warning("Couldn't run '%s' to gather environment information, giving up with 'bitbake -e':\n%s" % (cmd, err.output.decode('utf-8')))
+                return ''
 
 
     def load_bitbake_env(self, mach=None, target=None):
-- 
2.34.1