the build will now abort with an error message when an undefined build TARGET is named

Fixes #1938

Typo: Skyalke -> Skylake

Worth fixing, it gets in the way of searching....

Fix typo in UNKNOWN core name

Re-enable loop unrolling in trmv and remove the scary warning

fixes #1748 as that half of the fix for #1332 appears to have been an overreaction on my part.

Delete the pthread key on cleanup in TLS mode

already provided conditionally by common.h via openblas_utest.h
Unconditional inclusion breaks older Android and similar platforms that use OPENBLAS_COMPLEX_STRUCT

to avoid a crash when OpenBLAS was loaded via dlopen and libc tries to clean up the leaked TLS after dlclose
Fixes #1720

Should be of no consequence, right?

Add -fPIC to provided CFLAGS/FFLAGS if required

Fix thinko in skylake beta handling

casting ints is cheaper but it has a rounding, not memory casing effect, resulting in
invalid outcome

override user-provided FFLAGS if necessary

Add -mavx2 to TARGET=HASWELL builds

to leverage improvements from PR#1921

Reflect ARMV8 target definition changes from PR1876

and create config target directory for cross-compiles.

Avoid taking the root of a negative number in simple threaded syrk

Fixes #1924 where numpy 1.17+ would report the (transient) FE_INVALID exception raised for the domain error.

rebase

Replicate some of the SKYLAKEX dgemm improvements also to HASWELL

Haswell likes a GEMM_PREFERED_SIZE of 16 to improve the split that the
threading code does to make it a nice multiple of the SIMD kernel size

The dgemm_ncopy_8_skylakex.c code is not avx512 specific and gives
a nice performance boost for medium sized matrices

it's more efficient for certain tall/skinny matrices

(sgemm) Apply some of the SKYLAKEX optimizations also to HASWELL

sgemm_ncopy_4_skylakex.c uses SSE transpose operations where the
real perf win happens; this also works great for Haswell.

This gives double digit percentage gains on small and skinny matrices