bpo-45723: Detect missing pkg-config (GH-29442)

[tiran]

Signed-off-by: Christian Heimes christian@python.org

https://bugs.python.org/issue45723

[ned-deily]

Where is AC_PATH_TOOL being picked up from? The current PR doesn't work for me.

[ned-deily]

[...]
config.status: creating pyconfig.h
creating Modules/Setup.local
creating Makefile
pkg-config is missing. Some dependencies may not be detected correctly.
If you want a release build with all stable optimizations active (PGO, etc),
please run ./configure --enable-optimizations
$ pkg-config
Must specify package names on the command line
$ which pkg-config
/usr/bin/pkg-config

This is on a reasonably vanilla Debian system. Also the same on macOS with pkg-config installed from MacPorts.

[tiran]

Strange ... could you please paste the output of grep PKG_CONFIG config.log ?

My system (Fedora 34):

$ grep PKG_CONFIG config.log ac_cv_env_PKG_CONFIG_LIBDIR_set=
ac_cv_env_PKG_CONFIG_LIBDIR_value=
ac_cv_env_PKG_CONFIG_PATH_set=
ac_cv_env_PKG_CONFIG_PATH_value=
ac_cv_env_PKG_CONFIG_set=
ac_cv_env_PKG_CONFIG_value=
ac_cv_path_ac_pt_PKG_CONFIG=/usr/bin/pkg-config
ac_cv_prog_ac_ct_PKG_CONFIG=/usr/bin/pkg-config
PKG_CONFIG='/usr/bin/pkg-config'
PKG_CONFIG_LIBDIR=''
PKG_CONFIG_PATH=''

[tiran]

Where is AC_PATH_TOOL being picked up from? The current PR doesn't work for me.

AC_PATH_TOOL is provided by autoconf/programs.m4.

[tiran]

D'oh, I put test -n to test the output message and forgot to replace it with test -z.