Removed automated setting of USE_VFORK for macOS

The automatic setting of USE_VFORK in unix/configure.in is useless,
confusing, and deprecated. 

Background: configure.in had a section, where it sets
automatically USE_VFORK for macOS.

if test "`uname -s`" = "Darwin" ; then
...
    AC_DEFINE(USE_VFORK, 1, [Should we use vfork() instead of fork()?])
...

However, Daniel Steffen has added the following section 17 years ago
which effectively deactivated USE_VFORK for the x86_64 platform, when
it is set, due to a bug report in RDAR (Apple's bug tracking
system). 16 years ago a section was added to deactivate USE_VFORK for
all platforms with llvm-gcc-4.2 or newer.

/* 
 *---------------------------------------------------------------------------
 * At present, using vfork() instead of fork() causes execve() to fail
 * intermittently on Darwin x86_64. rdar://4685553
 *---------------------------------------------------------------------------
 */

/* Workaround problems with vfork() when building with llvm-gcc-4.2 */
            (__GNUC__ > 4 || (__GNUC__ == 4 && (__GNUC_MINOR__ > 2 || \
            (__GNUC_MINOR__ == 2 && __GNUC_PATCHLEVEL__ > 0))))

This means, that the last 17 years, USE_VFORK was not doing anything
on macOS. Furthermore, macOS 12 (Monterey, released 2021) deprecated
vfork() officially. 

Therefore, it is safe to remove the setting of USE_VFORK from the
default configuration for macOS.

It is still possible to set USE_VFORK manually for certain platform if
needed.

0 files changed, 0 insertions, 0 deletions