config: libintl/libiconv for gettext() detection

Detect in autoconf whether `-lintl` and possibly `-liconv` are necessary
for translation functions like `gettext()`.

The actual autoconf code is just:

```
AM_ICONV
AM_GNU_GETTEXT([external])
LIBS="$LIBS $LTLIBINTL $LTLIBICONV"
```

References:

https://www.gnu.org/software/gettext/manual/html_node/AM_005fGNU_005fGETTEXT.html
https://www.gnu.org/software/gettext/manual/html_node/AM_005fICONV.html

The reason to check for `libiconv` and add it separately is that this is
sometimes necessary if users are linking statically.

The `config/*.m4` files were added by running `gettextize` and removing
everything else.

The empty file `config/config.rpath` is necessary to avoid an error with
some versions of autotools, see:

http://ramblingfoo.blogspot.com/2007/07/required-file-configrpath-not-found.html

The `config.rpath` copied by `gettextize` does not currently work, there
is some kind of missing interaction with `libtool` and it tries to apply
`libtool` flags to the compiler.

Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed-by: Richard Laager <[email protected]>
Signed-off-by: Rafael Kitover <[email protected]>
Closes #8554 

1 files changed, 8 insertions, 0 deletions

diff --git a/config/user-gettext.m4 b/config/user-gettext.m4
new file mode 100644
index 000000000..89d1d45bf
--- /dev/null
+++ b/config/user-gettext.m4
@@ -0,0 +1,8 @@
+dnl #
+dnl # Check if libintl and possibly libiconv are needed for gettext() functionality
+dnl #
+AC_DEFUN([ZFS_AC_CONFIG_USER_GETTEXT], [
+    AM_ICONV
+    AM_GNU_GETTEXT([external])
+    LIBS="$LIBS $LTLIBINTL $LTLIBICONV"
+])