Merge changes Id711e387,I531a2ee1,Ic5b48514,I81f5f663,I6c529c13, ... into integration

* changes:
refactor(romlib): absorb WRAPPER_FLAGS into LDFLAGS
fix(build): simplify the -target options
fe

Merge changes Id711e387,I531a2ee1,Ic5b48514,I81f5f663,I6c529c13, ... into integration

* changes:
refactor(romlib): absorb WRAPPER_FLAGS into LDFLAGS
fix(build): simplify the -target options
feat(build): allow full LTO builds with clang
refactor(build): make sorting of sections generic
feat(build): use clang as a linker
fix(build): correctly detect that an option is missing with ld_option
feat(build): pass cflags to the linker when LTO is enabled

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feat(build): pass cflags to the linker when LTO is enabled

Usually, both compiling and linking happen by calling the top level
gcc/clang binary. Also, both compilers quite specifically tell us to
pa

feat(build): pass cflags to the linker when LTO is enabled

Usually, both compiling and linking happen by calling the top level
gcc/clang binary. Also, both compilers quite specifically tell us to
pass the same flags to the compilation and linking stages when we enable
LTO. This is crucial for things like the undefined behaviour sanitiser.
Anecdotally, in working on this, there have been a fair few errors that
the compiler has only been able to catch due to warning flags being
passed to the linker and building with LTO.

This patch puts the contents of TF_CFLAGS into TF_LDFLAGS when LTO is
enabled. This is easier said than done, however, as we support building
with clang and linking with gcc (or vice versa), so CFLAGS that are
discovered for one will not work for the other. This patch works around
this by splitting all flags into a per-compiler variable. Then CFLAGS
and LDFLAGS get the contents of the correct one.

Some notable side effects: CPPFLAGS and TF_CFLAGS_$(ARCH) become empty
and are removed, although expanding them is kept as platforms set them.
Some flags become duplicate and are removed form TF_LDFLAGS (eg -O1).

The errata (--fix) flags are kept as-is but moved to cpu-ops.mk for
consistency. This is because they currently don't work with LTO and will
be addressed in a later patch.

Finally, ERROR_DEPRECATED's flags are also identical on all compilers so
don't maintain a difference.

Change-Id: I3630729ee5f474c09d4722cd0ede6845e1725d95
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>

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Merge pull request #1686 from antonio-nino-diaz-arm/an/backtrace

backtrace: Extract rules from root Makefile

backtrace: Extract rules from root Makefile

It's better to have them in a separate file instead of having them spread
across the Makefile. This is what the stack protector is already doing.

Change-

backtrace: Extract rules from root Makefile

It's better to have them in a separate file instead of having them spread
across the Makefile. This is what the stack protector is already doing.

Change-Id: Id30742c0af10de5ea6d10674ca25bf52b0f2b262
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

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