Makefile: add NO_UTEST

[ffontaine]

Add NO_UTEST to allow the user to disable building utest

[martin-frbg]

Thanks - I wonder why you would want to do this ?

[ffontaine]

Because utest unconditonally uses fork resulting in the following build failure on toolchain without MMU:

test_fork.c:(.text+0x120): undefined reference to `fork'

Full build log: http://autobuild.buildroot.org/results/b9d/b9d097ae077f2cb40fc60de94bf25423636af005/build-end.log

[martin-frbg]

I see, so it is actually this one test that should be excluded as not supported on your platform. Does the uclibc toolchain define anything that could be used to shortcut the fork test ? (Assuming that everything else needed by the OpenBLAS library itself is implemented)

[ffontaine]

When MMU is disabled on an uclibc-ng toolchain, usr/include/bits/uClibc_config.h will contain:

#define __ARCH_HAS_MMU__ 1
#undef __ARCH_USE_MMU__

However, I still think that adding NO_UTEST is a better solution that adding uclibc-ng specific code to openblas. NO_UTEST could be used for example to speed up build time.
An other solution would be to add MMU dependency to openblas in buildroot.

[martin-frbg]

build should be fixed by #4544

[ffontaine]

Thanks, however, test_post_fork.c shall also be patched to fully fix the build failure:

test_post_fork.c:(.text+0xb4): undefined reference to `fork'

[martin-frbg]

sorry for that, now addressed in #4546

[ffontaine]

Thanks, build failure is fixed, closing this PR.