Improve the autoconf code for finding libtirpc and do not assume the
headers are in /usr/include/tirpc.
Also remove this assumption from the `rpc/xdr.h` header in libspl and
use the same `#include_next` mechanism that is used for other libspl
headers.
Include pkg.m4 from pkg-config in config/ for PKG_CHECK_MODULES(), the
file license allows this.
Include ax_save_flags.m4 and ax_restore_flags.m4 from autoconf-archive,
the file licenses are compatible. Use the 2012 versions so as not rely
on a more recent autoconf feature AS_VAR_COPY(), which breaks some build
slaves.
Add new macro library `config/find_system_library.m4` which defines the
FIND_SYSTEM_LIBRARY() macro which is a convenience wrapper over using
PKG_CHECK_MODULES() with a fallback to standard library locations and
some sanity checks.
The parameters are:
```
FIND_SYSTEM_LIBRARY(VARIABLE-PREFIX, MODULE, HEADER, HEADER-PREFIXES,
LIBRARY, FUNCTIONS, [ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND])
```
`HEADER-PREFIXES` and `FUNCTIONS` are comma-separated m4 lists.
For libtirpc we are using:
```
FIND_SYSTEM_LIBRARY(LIBTIRPC, [libtirpc], [rpc/xdr.h], [tirpc], [tirpc],
[xdrmem_create], [], [...])
```
The headers are first checked for without the prefixes and then with.
This system works with pkg-config and falls back on checking standard
header/library locations, it can be easily overridden by the user by
setting the `PREFIX_CFLAGS` and `PREFIX_LIBS` variables which are
automatically added to the `./configure --help` output.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rafael Kitover <rkitover@gmail.com>
Closes#7422Closes#8313
762f9ef3d9