makefiles/toolchain: fix command -v multiple commands

[cladmi]

Contribution description

command -v first second third only works in bash and not in sh.
So replace with multiple calls to command.

This fixes using objcopy when the toolchain objcopy is not available.

Testing procedure

I found this when building in docker with a machine without toolchain.

If you have your arm toolchain installed outside of the normal path you can try with the same procedure of changing the PATH.
Or use another board you do not have the toolchain for.

With this PR

It fallback to objcopy:

BOARD=samr21-xpro PATH=/usr/bin:/bin make --no-print-directory -C examples/hello-world/ info-debug-variable-OBJCOPY
/bin/sh: 1: arm-none-eabi-gcc: not found
/usr/bin/objcopy

TOOLCHAIN=llvm BOARD=samr21-xpro PATH=/usr/bin:/bin make --no-print-directory -C examples/hello-world/ info-debug-variable-OBJCOPY
/bin/sh: 1: arm-none-eabi-gcc: not found
/usr/bin/objcopy

Original behavior is kept:

BOARD=samr21-xpro  make --no-print-directory -C examples/hello-world/ info-debug-variable-OBJCOPY
/opt/gcc-arm-none-eabi-7-2018-q2-update/bin/arm-none-eabi-objcopy

TOOLCHAIN=llvm BOARD=samr21-xpro  make --no-print-directory -C examples/hello-world/ info-debug-variable-OBJCOPY
/opt/gcc-arm-none-eabi-7-2018-q2-update/bin/arm-none-eabi-objcopy

The arm-none-eabi-gcc error is unrelated to this PR and I think is related to #10850 and is also present in master.

Behavior in master

Master does not fallback to objcopy.

BOARD=samr21-xpro PATH=/usr/bin:/bin make --no-print-directory -C examples/hello-world/ info-debug-variable-OBJCOPY
/bin/sh: 1: arm-none-eabi-gcc: not found
/home/harter/work/git/RIOT/makefiles/toolchain/gnu.inc.mk:18: objcopy not found. Hex file will not be created.
true
 TOOLCHAIN=llvm BOARD=samr21-xpro PATH=/usr/bin:/bin make --no-print-directory -C examples/hello-world/ info-debug-variable-OBJCOPY
/bin/sh: 1: arm-none-eabi-gcc: not found
/home/harter/work/git/RIOT/makefiles/toolchain/llvm.inc.mk:25: objcopy not found. Hex file will not be created.
true

Normal behavior was the same

BOARD=samr21-xpro  make --no-print-directory -C examples/hello-world/ info-debug-variable-OBJCOPY
/opt/gcc-arm-none-eabi-7-2018-q2-update/bin/arm-none-eabi-objcopy
TOOLCHAIN=llvm BOARD=samr21-xpro  make --no-print-directory -C examples/hello-world/ info-debug-variable-OBJCOPY
/opt/gcc-arm-none-eabi-7-2018-q2-update/bin/arm-none-eabi-objcopy

Low level justification

Difference between bash and sh and make uses sh by default.

sh -c 'command -v this does not exist false true'
# nothing is printed

bash -c 'command -v this does not exist false true'
false
true

Issues/PRs references

I notified this in #10870

Follow ups

Other boards/cpus are defining objcopy and other toolchains in their own Makefile.include when they should be using this one. It also goes for all the compiler variables.

[cladmi]

Another update could be to define true as fallback anyway and do not print a warning.

[emmanuelsearch]

Tested on OS X, this is what I get, so... no change compared to master?

MacBookEmmanuel:RIOT emmanuel$ BOARD=samr21-xpro PATH=/usr/bin:/bin make --no-print-directory -C examples/hello-world/ info-debug-variable-OBJCOPY
bash: arm-none-eabi-gcc: command not found
/Users/emmanuel/Documents/work/CODING/RIOT/makefiles/toolchain/gnu.inc.mk:18: objcopy not found. Hex file will not be created.
true
MacBookEmmanuel:RIOT emmanuel$ TOOLCHAIN=llvm BOARD=samr21-xpro PATH=/usr/bin:/bin make --no-print-directory -C examples/hello-world/ info-debug-variable-OBJCOPY
bash: arm-none-eabi-gcc: command not found
/Users/emmanuel/Documents/work/CODING/RIOT/makefiles/toolchain/llvm.inc.mk:25: objcopy not found. Hex file will not be created.
true
MacBookEmmanuel:RIOT emmanuel$ BOARD=samr21-xpro  make --no-print-directory -C examples/hello-world/ info-debug-variable-OBJCOPY
/opt/arm-none-eabi-gcc-6-q2/bin/arm-none-eabi-objcopy
MacBookEmmanuel:RIOT emmanuel$ TOOLCHAIN=llvm BOARD=samr21-xpro  make --no-print-directory -C examples/hello-world/ info-debug-variable-OBJCOPY
/opt/arm-none-eabi-gcc-6-q2/bin/arm-none-eabi-objcopy

[cladmi]

We checked IRL, and @emmanuelsearch does not have objcopy or gobjcopy installed. Which looks common on mac according to

RIOT/boards/native/Makefile.include

Lines 28 to 33 in 782b181

	ifeq (0,$(shell which gobjcopy 2>&1 > /dev/null ; echo $$?))
	export OBJCOPY ?= gobjcopy
	else
	# If gobjcopy is not available, just do nothing. The hexfile
	# is not used for native anyways.
	export OBJCOPY ?= true

When replacing the last objcopy by objdump for example, we correctly fallback to objdump.
So this PR allows to fallback on mac. Did not tested the behavior on master.

[smlng]

tested, works on macOS too (just to be sure).

Side node: looks like some tools should be queried for in a more central part of the build system than twice (the same) for gcc and llvm.

[smlng]

btw. I have gobjcopy and other installed

[cladmi]

We noticed with @jcarrano while discussing this, that the case from master was working on his machine as on ArchLinux SHELL=/bin/bash by default in Make.