patch to __attribute__ ((visibility ("default"))) on exported functions

[mattip]

• I updated the package version in pyproject.toml and made sure the first 3 numbers match git describe --tags --abbrev=8 in OpenBLAS at the OPENBLAS_COMMIT. If I did not update OPENBLAS_COMMIT, I incremented the wheel build number (i.e. 0.3.29.0.0 to 0.3.29.0.1)

This is a proof of concept that works to hide functions from exposing them from the shared object on posix

• Use CFLAGS+=-fhidden to hide by default
• Add __attribute__ ((visibility ("default"))) in all the exported function definitions
• Use NO_LAPACKE=1 to avoid building (and exporting) legacy lapack routines

For me this solves numpy/numpy#30299, it no longer segfaults. Although when I look at ltrace I still see that a global openblas is overriding the function dgemm_kernel_HASWELL in the call to scipy_cblas_dgemm64_ at NumPy import.

[mattip]

global openblas is overriding the function dgemm_kernel_HASWELL

I added the hidden directive to the PROLOGUE macro for assembler code, and in doing so discovered that there is assembler code for

• int lsame(char *a, char *b) which compares *a == *b
• FLOAT cabs(FLOAT *a) which does fabs(a[0]) + fabs(a[1]).

Both these functions have generic equivalents in the kernels/generics directory, and I checked on Compiler Explorer that modern compilers generate equivalent assembler to the hand-created assembler in the non-generic directories. So rather than create a special non-hidden assembler PROLOGUE macro, I set the build to use the generic C versions, which can easily be marked with the visible attribute.