[PATCH v2] kbuild: use printf instead of echo -e extension

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

We are using echo -e, so the \n in the string being echo'd are
interpreted. As -e is not POSIX and dash doesn't provide it,
we use a strange /usr/bin/env echo -e construct hoping that
whatever non-builtin echo is first in the search path supports -e.

As the new lines are just used to separate CPP directives, we can
just pass the directives as $(CPP) flags. This has the same result,
but is potable and avoids NixOS complaining when building barebox.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
v1 -> v2:
  - drop echo -e eltogether after Sascha pointed out why it needs
    /usr/bin/env.

Tested with two fragments:
  - dts variable is defined for the DT it references
  - fragments are included (checked with #warning)
  - fragment change triggers rebuild
  - original DT change triggers rebuild
  - fragmentless case works ok
    
 scripts/Makefile.lib | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 4deaa5dfa73c..befd47ed6600 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -372,8 +372,8 @@ $(obj)/%.dtb.z: $(obj)/%.dtb FORCE
 dts-frags = $(subst $(quote),,$(CONFIG_EXTERNAL_DTS_FRAGMENTS))
 quiet_cmd_dtc = DTC     $@
 # For compatibility between make 4.2 and 4.3
-cmd_dtc = /usr/bin/env echo -e '$(pound)define $(subst -,_,$(*F))_dts 1\n'$(foreach f,$< $(2),'$(pound)include "$(f)"\n') | \
-	$(CPP) $(dtc_cpp_flags) -x assembler-with-cpp -o $(dtc-tmp) - ; \
+cmd_dtc = echo | $(CPP) $(dtc_cpp_flags) -x assembler-with-cpp -o $(dtc-tmp) \
+	-D'$(subst -,_,$(*F))_dts=1' $(foreach f,$< $(2),-include '$(f)') - ; \
 	$(objtree)/scripts/dtc/dtc -O dtb -o $@ -b 0 \
 		-i $(srctree)/arch/$(SRCARCH)/dts $(DTC_FLAGS) \
 		-i $(srctree)/dts/src/$(SRCARCH) \
-- 
2.39.2