In FDPIC mode, we set -fPIE unless the user provides -fno-PIE, -fpie,
-fPIC or -fpic: indeed FDPIC code is PIC, but we want to generate code
for executables rather than shared libraries by default.

We also make sure to use the --fdpic assembler option, and select the
appropriate linker emulation.

At link time, we also default to -pie, unless we are generating a
shared library or a relocatable file (-r). Note that static link is
not supported as it requires specifying the dynamic linker because the
executable still has to relocate itself at startup.

We also force 'now' binding since lazy binding is not supported.

We should also apply the same behavior for -Wl,-Ur as for -r, but I
couldn't find how to describe that in the specs fragment.

2019-09-10  Christophe Lyon  <christophe.lyon@st.com>
	Mickaël Guêné <mickael.guene@st.com>

	gcc/
	* config.gcc: Handle arm*-*-uclinuxfdpiceabi.
	* config/arm/bpabi.h (TARGET_FDPIC_ASM_SPEC): New.
	(SUBTARGET_EXTRA_ASM_SPEC): Use TARGET_FDPIC_ASM_SPEC.
	* config/arm/linux-eabi.h (FDPIC_CC1_SPEC): New.
	(CC1_SPEC): Use FDPIC_CC1_SPEC.
	(MUSL_DYNAMIC_LINKER): Add -fdpic suffix when needed.
	* config/arm/uclinuxfdpiceabi.h: New file.

	libsanitizer/
	* configure.tgt (arm*-*-*fdpiceabi): Sanitizers are
	unsupported in this configuration.



Co-Authored-By: Mickaël Guêné <mickael.guene@st.com>

From-SVN: r275565