[Vm-dev] [OpenSmalltalk/opensmalltalk-vm] 7f69e4: Listen to feature_test_macros(7) with a guard.

[Tobias Pape]

  Branch: refs/heads/Cog
  Home:   https://github.com/OpenSmalltalk/opensmalltalk-vm
  Commit: 7f69e44dd9cdf5d1fe2d838e824e86f7503abe93
      https://github.com/OpenSmalltalk/opensmalltalk-vm/commit/7f69e44dd9cdf5d1fe2d838e824e86f7503abe93
  Author: Tobias Pape <tobias at netshed.de>
  Date:   2021-04-04 (Sun, 04 Apr 2021)

  Changed paths:
    M platforms/Cross/vm/sq.h

  Log Message:
  -----------
  Listen to feature_test_macros(7) with a guard.

If HAVE_CONFIG_H is given (most presumably on the command line)
it is safe to include the (#define-only) config.h.
On prominent platforms, these defines must precede any inlcudes.
To quote feature_test_macros(7) on Linux:

> NOTE:  In  order to be effective, a feature test macro must be defined before including any header files.

config.h provides these macros, either manually specified or
through means of configuration (eg. autoconf/configure).

Having these defines early does not hurt platforms not using this
system but is vital on platforms using it.