[scarthgap PATCH 6/7] external-arm-toolchain: override dynamic loader path with usrmerge enabled

usrmerge nowaday required by systemd [1] but it broke
external-arm-toolchain in several ways...

When usrmerge is enabled, /lib is no longer part of SYSROOT_DIRS list
while the prebuilt toolchain expect the dynamic loader to be placed in
/lib not /usr/lib.

There is no /lib directory in the per-package sysroot directory
generated to build each package:

  [...]/build/tmp/sysroots-components/<target>/<package>/
  sysroot-providers/ usr/

But the cross-compiler still generate binaries with dynamic loarder
path set to "/lib/ld-linux-<target>.so*"

  strings sanitycheckc_cross.exe | grep ld
  /lib/ld-linux-aarch64.so.1

A symlink /lib -> /usr/lib is crated in the final rootfs image.

But this broke the meson-qemuwrapper used when "qemu-usermode"
(MACHINE_FEATURES) is available:

See [2]:
  do_write_config:append:class-target() {
       # Write out a qemu wrapper that will be used as exe_wrapper so that meson
       # can run target helper binaries through that.
       qemu_binary="${@qemu_wrapper_cmdline(d, '$STAGING_DIR_HOST', ['$STAGING_DIR_HOST/${libdir}','$STAGING_DIR_HOST/${base_libdir}'])}"

It produce a runtime issue while running a meson sanity check:

  meson-qemuwrapper [...]/build/meson-private/sanitycheckc_cross.exe

  qemu-aarch64: Could not open '/lib/ld-linux-aarch64.so.1': No such file or directory

Note: The binaries build by the Yocto internal toolchain seems be "patched" [3]
to look at /usr/lib instead of /lib.

We use -Wl,--dynamic-linker to make sure that the cross-compiler
generate binaries using the dynamic loader path defined by usrmerge
for all packages build by Yocto.

[1] https://git.openembedded.org/openembedded-core/commit/?id=802e853eeddf16d73db1900546cc5f045d1fb7ed
[2] https://git.openembedded.org/openembedded-core/tree/meta/classes-recipe/meson.bbclass?h=2024-04.3-scarthgap#n130
[3] https://github.com/openembedded/openembedded-core/blob/scarthgap/meta/recipes-devtools/gcc/gcc/0007-Define-GLIBC_DYNAMIC_LINKER-and-UCLIBC_DYNAMIC_LINKE.patch

Signed-off-by: Romain Naour <[email protected]>
Acked-by: Denys Dmytriyenko <[email protected]>
Signed-off-by: Jon Mason <[email protected]>
(cherry picked from commit cb4c0c9a937046c9effdeeff2496d52866c64197)
Signed-off-by: Romain Naour <[email protected]>
---
 .../conf/distro/include/tcmode-external-arm.inc              | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/meta-arm-toolchain/conf/distro/include/tcmode-external-arm.inc b/meta-arm-toolchain/conf/distro/include/tcmode-external-arm.inc
index 898663ea..99fe56b8 100644
--- a/meta-arm-toolchain/conf/distro/include/tcmode-external-arm.inc
+++ b/meta-arm-toolchain/conf/distro/include/tcmode-external-arm.inc
@@ -15,6 +15,11 @@ EAT_TARGET_SYS:aarch64 ?= "${@ 'aarch64-none-linux-gnu' if os.path.exists('${EXT
 EAT_TARGET_SYS = "${TARGET_SYS}"
 TARGET_PREFIX = "${EAT_TARGET_SYS}-"
 
+EXTERNAL_TOOLCHAIN_LIBDIR = "${@bb.utils.contains('DISTRO_FEATURES', 'usrmerge', '/usr/lib', '/lib', d)}"
+EXTERNAL_TOOLCHAIN_DYN_LINKER_PATH:arm ?= " -Wl,--dynamic-linker=${EXTERNAL_TOOLCHAIN_LIBDIR}/ld-linux-armhf.so.3"
+EXTERNAL_TOOLCHAIN_DYN_LINKER_PATH:aarch64 ?= " -Wl,--dynamic-linker=${EXTERNAL_TOOLCHAIN_LIBDIR}/ld-linux-aarch64.so.1"
+TARGET_LDFLAGS:append:class-target = "${EXTERNAL_TOOLCHAIN_DYN_LINKER_PATH}"
+
 EAT_LIBDIR:arm = "lib"
 EAT_LIBDIR:aarch64 = "lib64"
 
-- 
2.47.1