[L/unstable 02/13] UBUNTU: [Packaging] Make the compiler for fix-filenames explicit

[Masahiro Yamada]

The rule for debian/scripts/fix-filenames:

        $(CC) -o $@ $^

is fragile because 'CC' is not set anywhere in our Makefiles.

We rely on GNU Make using 'CC' in its internal database. This assumption
would break if the -R option is given. In this case, the line above
would expand to:

        -o $@ $^

What is worse, GNU Make ignores errors if the recipe line starts with '-'.
(See the note below)

Then, GNU Make would proceed without building fix-filenames.

  $ debian/rules -R debian/scripts/fix-filenames
  o debian/scripts/fix-filenames debian/scripts/fix-filenames.c
  /bin/bash: line 1: o: command not found
  make: [debian/rules.d/2-binary-arch.mk:17: debian/scripts/fix-filenames] Error 127 (ignored)

Make the compiler explicit, and change the posion of -o to make it even
robust.

[Note]

Make manual "5.5 Errors in Recipes" [1] says:

  To ignore errors in a recipe line, write a ‘-’ at the beginning of the
  line’s text (after the initial tab). The ‘-’ is discarded before the
  line is passed to the shell for execution.

[1]: https://www.gnu.org/software/make/manual/make.html#Errors

Signed-off-by: Masahiro Yamada <masahiro.yamada at canonical.com>
---
 debian/rules.d/0-common-vars.mk | 4 +++-
 debian/rules.d/2-binary-arch.mk | 2 +-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/debian/rules.d/0-common-vars.mk b/debian/rules.d/0-common-vars.mk
index 1d8f8b85772f..c0910d46670a 100644
--- a/debian/rules.d/0-common-vars.mk
+++ b/debian/rules.d/0-common-vars.mk
@@ -251,10 +251,12 @@ conc_level		= -j$(CONCURRENCY_LEVEL)
 
 PYTHON ?= $(firstword $(wildcard /usr/bin/python3) $(wildcard /usr/bin/python2) $(wildcard /usr/bin/python))
 
+HOSTCC ?= $(DEB_BUILD_GNU_TYPE)-$(gcc)
+
 # target_flavour is filled in for each step
 kmake = make ARCH=$(build_arch) \
 	CROSS_COMPILE=$(CROSS_COMPILE) \
-	HOSTCC=$(DEB_BUILD_GNU_TYPE)-$(gcc) \
+	HOSTCC=$(HOSTCC) \
 	CC=$(CROSS_COMPILE)$(gcc) \
 	KERNELVERSION=$(abi_release)-$(target_flavour) \
 	CONFIG_DEBUG_SECTION_MISMATCH=y \
diff --git a/debian/rules.d/2-binary-arch.mk b/debian/rules.d/2-binary-arch.mk
index 9d2ded9cdee1..56353ff6165f 100644
--- a/debian/rules.d/2-binary-arch.mk
+++ b/debian/rules.d/2-binary-arch.mk
@@ -14,7 +14,7 @@ endif
 shlibdeps_opts = $(if $(CROSS_COMPILE),-- -l$(CROSS_COMPILE:%-=/usr/%)/lib)
 
 debian/scripts/fix-filenames: debian/scripts/fix-filenames.c
-	$(CC) -o $@ $^
+	$(HOSTCC) $^ -o $@
 
 $(stampdir)/stamp-prepare-%: config-prepare-check-%
 	@echo Debug: $@
-- 
2.34.1