HAVE_LIBNUMA is defined as non-zero even when libnuma does not exist

I think this is a regression introduced in the last few weeks.

The libnuma dependency is checked correctly by the configure script, but somehow when I don't have libnuma installed I still have HAVE_LIBNUMA defined as non-zero so I end up with this error:

/usr/bin/x86_64-linux-gnu-ld.gold: error: cannot find -lnuma

rts/posix/OSMem.c:368:0: error:
     error: undefined reference to 'mbind'
    |
368 |     if (RtsFlags.GcFlags.numa) {
    | ^

rts/posix/OSMem.c:670:0: error:
     error: undefined reference to 'numa_num_configured_nodes'
    |
670 | }
    | ^

rts/posix/OSMem.c:680:0: error:
     error: undefined reference to 'numa_get_mems_allowed'
    |
680 |
    | ^

rts/posix/OSMem.c:670:0: error:
     error: undefined reference to 'numa_num_configured_nodes'
    |
670 | }
    | ^

rts/posix/OSMem.c:685:0: error:
     error: undefined reference to 'numa_bitmask_free'
    |
685 |     mask = numa_get_mems_allowed();
    | ^

rts/posix/OSMem.c:670:0: error:
     error: undefined reference to 'numa_num_configured_nodes'
    |
670 | }
    | ^
collect2: error: ld returned 1 exit status
`gcc' failed in phase `Linker'. (Exit code: 1)
utils/ghc-cabal/ghc.mk:56: recipe for target 'utils/ghc-cabal/dist/build/tmp/ghc-cabal' failed

Installing libnuma-dev fixes this.

Relevant lines in config.log:

CabalHaveLibNuma='False'
#define HAVE_LIBNUMA 0

I have no idea why HAVE_LIBNUMA is not 0 when compiling the file.

Trac metadata

Trac field	Value
Version	8.6.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Build System
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