[ARM/FDPIC v6 13/24] [ARM] FDPIC: Force LSB bit for PC in Cortex-M architecture

[ARM/FDPIC v6 13/24] [ARM] FDPIC: Force LSB bit for PC in Cortex-M  architecture

Without this, when we are unwinding across a signal frame we can jump
to an even address which leads to an exception.

This is needed in __gnu_persnality_sigframe_fdpic() when restoring the
PC from the signal frame since the PC saved by the kernel has the LSB
bit set to zero.

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

	libgcc/
	* config/arm/unwind-arm.c (_Unwind_VRS_Set): Handle thumb-only
	architecture.

Co-Authored-By: Mickaël Guêné <mickael.guene@st.com>
From-SVN: r275575