picolib: Add (optional) rp2040 support to ARM TLS code #2

Job	Run time
cache-maker	5m 58s
minsize-linux (./.github/do-linux)	1h 58m 29s
minsize-linux (-Dio-float-exact=false -Dio-long-long=true -Dio-percent-b=true -Dio-long-double=tr...	1h 32m 12s
minsize-linux (-Dformat-default=integer -Dfreestanding=true -Dposix-io=false -Dnewlib-obsolete-ma...	1h 49m 43s
minsize-linux (-Dtinystdio=false, ./.github/do-linux)	1h 9m 41s
release-linux (./.github/do-linux)	1h 58m 55s
cmake-linux (./.github/do-cmake-linux -DCMAKE_BUILD_TYPE=RelWithDebInfo)	10m 3s
minsize-linux (-Dtinystdio=false -Dnewlib-io-float=true -Dio-long-long=true -Dio-long-double=true...	54m 0s
release-linux (-Dio-float-exact=false -Dio-long-long=true -Dio-percent-b=true -Dio-long-double=tr...	1h 39m 3s
cmake-linux (./.github/do-cmake-linux -DCMAKE_BUILD_TYPE=MinSizeRel)	10m 45s
release-linux (-Dformat-default=integer -Dfreestanding=true -Dposix-io=false -Dnewlib-obsolete-ma...	1h 54m 22s
cmake-linux (-D__IO_FLOAT=y -D_IO_FLOAT_EXACT=n -D_WANT_IO_LONG_LONG=y -D_MB_CAPABLE=y -D_WANT_IO...	9m 41s
release-linux (-Dtinystdio=false, ./.github/do-linux)	1h 15m 37s
cmake-linux (-D__IO_FLOAT=y -D_IO_FLOAT_EXACT=n -D_WANT_IO_LONG_LONG=y -D_MB_CAPABLE=y -D_WANT_IO...	9m 22s
release-linux (-Dtinystdio=false -Dnewlib-io-float=true -Dio-long-long=true -Dio-long-double=true...	55m 12s
	15h 53m 3s

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