[PATCH] Makefile: fix u-boot-initial-env target if lto is enabled

[Max Krummenacher]

From: Max Krummenacher <max.krummenacher at toradex.com>

With LTO enabled the U-Boot initial environment is no longer stored
in an easy accessible section in env/common.o. I.e. the section name
changes from build to build, its content maybe compressed and it is
annotated with additional data.

For GCC adding the option '-ffat-lto-objects' when compiling common.o
adds additionally the traditional sections in the object file and
'make u-boot-initial-env' would work also for the LTO enabled case.
However clang doesn't have that option.

Fix this by recompiling common.o into a object file only used for
the creation of u-boot-initial-env if LTO is enabled.

See also:
https://lore.kernel.org/all/927b122e-1f62-e790-f5ca-30bae4332c77@foss.st.com/

Signed-off-by: Max Krummenacher <max.krummenacher at toradex.com>

---

 Makefile | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/Makefile b/Makefile
index 3866cc62f9a..cd45c720d23 100644
--- a/Makefile
+++ b/Makefile
@@ -2451,9 +2451,17 @@ endif
 	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost
 
 quiet_cmd_genenv = GENENV  $@
+ifeq ($(LTO_ENABLE),y)
+cmd_genenv = $(CC) $(filter-out $(LTO_CFLAGS),$(c_flags)) -c -o env/initial_env.o env/common.c; \
+	$(OBJCOPY) --dump-section .rodata.default_environment=$@ env/initial_env.o; \
+	sed --in-place -e 's/\x00/\x0A/g' $@; sed --in-place -e '/^\s*$$/d' $@; \
+	sort --field-separator== -k1,1 --stable $@ -o $@; \
+	rm -f env/initial_env.o env/initial_env.su
+else
 cmd_genenv = $(OBJCOPY) --dump-section .rodata.default_environment=$@ env/common.o; \
 	sed --in-place -e 's/\x00/\x0A/g' $@; sed --in-place -e '/^\s*$$/d' $@; \
 	sort --field-separator== -k1,1 --stable $@ -o $@
+endif
 
 u-boot-initial-env: u-boot.bin
 	$(call if_changed,genenv)
-- 
2.35.3