This commit fixes building the "btree" example natmod on RV32 when
Picolibc is being used and uses thread-local storage for storing the
errno variable.
The fix is surprisingly simple: Picolibc allows overriding the function
that will provide a pointer to the "errno" variable, and the btree
natmod integration code already has all of this machinery set up as part
of its library integration. Redirecting Picolibc to the already
existing pointer provider function via a compile-time definition is
enough to let the module compile and pass QEMU tests.
This workaround will work on any Picolibc versions (Arm, RV32, Xtensa,
etc.) even if TLS support was not enabled to begin with, and will
effectively do nothing if the toolchain used will rely on Newlib to
provide standard C library functions.
Given that the btree module now builds and passes the relevant natmod
tests, said module is now part of the QEMU port's natmod testing
procedure, and CI now will build the btree module for RV32 as part to
its checks.
Signed-off-by: Alessandro Gatti <a.gatti@frob.it>
b63e528076