[OE-core] [PATCH] image/populate_sdk: Ensure symlinks in target sysroot are relative

[Richard Purdie]

In the target sysroot of an SDK we can have target system absolute links
which don't make sense. This adds a script which fixes them up to become relative
paths instead.

[YOCTO #5020]

Signed-off-by: Richard Purdie <richard.purdie at linuxfoundation.org>
---
diff --git a/meta/classes/image.bbclass b/meta/classes/image.bbclass
index 4a0946c..f1e62f14 100644
--- a/meta/classes/image.bbclass
+++ b/meta/classes/image.bbclass
@@ -4,7 +4,7 @@ inherit populate_sdk_base
 
 TOOLCHAIN_TARGET_TASK += "${PACKAGE_INSTALL}"
 TOOLCHAIN_TARGET_TASK_ATTEMPTONLY += "${PACKAGE_INSTALL_ATTEMPTONLY}"
-POPULATE_SDK_POST_TARGET_COMMAND += "rootfs_install_complementary populate_sdk; "
+POPULATE_SDK_POST_TARGET_COMMAND += "rootfs_install_complementary populate_sdk; rootfs_sysroot_relativelinks; "
 
 inherit gzipnative
 
@@ -617,6 +617,11 @@ rootfs_trim_schemas () {
 	done
 }
 
+# Make any absolute links in a sysroot relative
+rootfs_sysroot_relativelinks () {
+	sysroot-relativelinks.py ${SDK_OUTPUT}/${SDKTARGETSYSROOT}
+}
+
 EXPORT_FUNCTIONS zap_root_password remove_init_link do_rootfs make_zimage_symlink_relative set_image_autologin rootfs_update_timestamp rootfs_no_x_startup
 
 do_fetch[noexec] = "1"
diff --git a/scripts/sysroot-relativelinks.py b/scripts/sysroot-relativelinks.py
new file mode 100755
index 0000000..2e13744
--- /dev/null
+++ b/scripts/sysroot-relativelinks.py
@@ -0,0 +1,31 @@
+#!/usr/bin/env python
+import sys
+import os
+
+# Take a sysroot directory and turn all the abolute symlinks and turn them into
+# relative ones such that the sysroot is usable within another system.
+
+if len(sys.argv) != 2:
+    print("Usage is " + sys.argv[0] + "<directory>")
+    sys.exit(1)
+
+topdir = sys.argv[1]
+topdir = os.path.abspath(topdir)
+
+def handlelink(filep, subdir):
+    link = os.readlink(filep)
+    if link[0] != "/":
+        return
+    if link.startswith(topdir):
+        return
+    #print("Replacing %s with %s for %s" % (link, topdir+link, filep))
+    print("Replacing %s with %s for %s" % (link, os.path.relpath(topdir+link, subdir), filep))
+    os.unlink(filep)
+    os.symlink(os.path.relpath(topdir+link, subdir), filep)
+
+for subdir, dirs, files in os.walk(topdir):
+    for f in files:
+        filep = os.path.join(subdir, f)
+        if os.path.islink(filep):
+            #print("Considering %s" % filep)
+            handlelink(filep, subdir)