As described in bug report #75722, the configure script (acinclude.m4)
currently searches for the valgrind header file and enables valgrind
support if found.
When cross-compiling the searched paths are invalid for the target
platform because they belong to the host system. At the moment, there is
no way to tell the build system a dedicated path where to look for the
header file.
This leads to the issue, that when cross-compiling eg. for ARMv5 platform,
that valgrind header file is detected - e.g. because host system is amd64 -
and support is enabled - but target platform will never support valgrind
(valgrind requires e.g. at least ARMv7).
This change reworks the detection so that user could manually opt-in
valgrind support and optionally specify a directory where the build system
should look for the header file using the --with-valgrind option.
configure.ac was introduced in 2001 with automake-1.15 and autoconf-2.50
to replace the file named configure.in.
Autotools is preparing to remove configure.in in Automake 2.0.
All new software should be using configure.ac.
This also fixes Bug #69770 where extensions are creating configure.in
Signed-off-by: Brian Evans <grknight@gentoo.org>
