arm: Fix the mve multilib for the broken cmse support (pr99939).

arm: Fix the mve multilib for the broken cmse support (pr99939).

The current CMSE support in the multilib build for
"-march=armv8.1-m.main+mve -mfloat-abi=hard -mfpu=auto" is broken
as specified in PR99939 and this patch fixes the issue.

gcc/testsuite/ChangeLog:

2021-06-11  Srinath Parvathaneni  <srinath.parvathaneni@arm.com>

	PR target/99939
	* gcc.target/arm/cmse/cmse-18.c: Add separate scan-assembler
	directives check for target is v8.1-m.main+mve or not before
	comparing the assembly output.
	* gcc.target/arm/cmse/cmse-20.c: New test.

libgcc/ChangeLog:

2021-06-11  Srinath Parvathaneni  <srinath.parvathaneni@arm.com>

	PR target/99939
	* config/arm/cmse_nonsecure_call.S: Add	__ARM_FEATURE_MVE
	macro.
	* config/arm/t-arm: To link cmse.o and cmse_nonsecure_call.o
	on passing -mcmse option.