arm: Fix CMSE support detection in libgcc (PR target/99157)
As discussed in the PR, the Makefile fragment lacks a double '$' to
get the return-code from GCC invocation, resulting is CMSE support
missing from multilibs.
I checked that the simple patch proposed in the PR fixes the problem.
2021-02-23 Christophe Lyon <christophe.lyon@linaro.org>
Hau Hsu <hsuhau617@gmail.com>
PR target/99157
libgcc/
* config/arm/t-arm: Fix cmse support detection.