build-sys: Give sensible errors if missing pkg-config
pkg-config is used to find various libraries used by procps.
Unfortunately it, or rather automake, give terrible misleading
error messages if pkg-config is not installed.
At ./configure time you get this:
configure: error: ncurses support missing/incomplete (for partial
build use --without-ncurses)
At automake time you get this:
configure.ac:33: error: possibly undefined macro: AC_MSG_ERROR
If this token and others are legitimate, please use m4_pattern_allow.
See the Autoconf documentation.
configure.ac:48: error: possibly undefined macro: AS_IF
configure.ac:113: error: possibly undefined macro: AC_DEFINE
The internet is filled with such wonderful other examples.
This commit does two things:
At autoconf time, check PKG_PREREQ macro is defined which is found in
pkg.m4 and tells us pkg-config has its macros available.
At configure time, check the result of the pkg-config test and error
if it didn't find it.
Now it actually says its missing pkg-config. To be fair, the autoconf
check is "documented" and recommended in pkg.m4 file.
Signed-off-by: Craig Small <csmall@dropbear.xyz>