configure: fix cross pkg-config detection

When cross-compiling, CURL_CHECK_PKGCONFIG was checking for the cross
pkg-config using ${host}-pkg-config.

The gold standard for doing this correctly is pkg-config's own macro,
PKG_PROG_PKG_CONFIG.  However, on the assumption that you have a good
reason not to use that directly (reduced dependencies for maintainer
builds?), the behaviour of cURL's version should at least match.
PKG_PROG_PKG_CONFIG uses AC_PATH_TOOL, which ultimately ends up trying
${host_alias}-pkg-config; this is not quite the same as what cURL does,
and may differ because ${host} has been run through config.sub.  For
instance, when cross-building to the armhf architecture on Ubuntu,
${host_alias} is arm-linux-gnueabihf while ${host} is
arm-unknown-linux-gnueabihf.  This may also have been the cause of the
problem reported at http://curl.haxx.se/mail/lib-2012-04/0224.html.

AC_PATH_TOOL is significantly simpler than cURL's current code, and
dates back to well before the current minimum of Autoconf 2.57, so let's
use it instead.

diff --git a/acinclude.m4 b/acinclude.m4
index 6596be7..c36576a 100644 (file)
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -3256,8 +3256,8 @@ AC_DEFUN([CURL_EXPORT_PCDIR], [
 
 dnl CURL_CHECK_PKGCONFIG ($module, [$pcdir])
 dnl ------------------------
-dnl search for the pkg-config tool (if not cross-compiling). Set the PKGCONFIG
-dnl variable to hold the path to it, or 'no' if not found/present.
+dnl search for the pkg-config tool. Set the PKGCONFIG variable to hold the
+dnl path to it, or 'no' if not found/present.
 dnl
 dnl If pkg-config is present, check that it has info about the $module or
 dnl return "no" anyway!
@@ -3269,15 +3269,7 @@ AC_DEFUN([CURL_CHECK_PKGCONFIG], [
 
     PKGCONFIG="no"
 
-    if test x$cross_compiling = xyes; then
-      dnl see if there's a pkg-specific for this host setup
-      AC_PATH_PROG( PKGCONFIG, ${host}-pkg-config, no,
-                    $PATH:/usr/bin:/usr/local/bin)
-    fi
-
-    if test x$PKGCONFIG = xno; then
-      AC_PATH_PROG( PKGCONFIG, pkg-config, no, $PATH:/usr/bin:/usr/local/bin)
-    fi
+    AC_PATH_TOOL( PKGCONFIG, pkg-config, no, $PATH:/usr/bin:/usr/local/bin)
 
     if test x$PKGCONFIG != xno; then
       AC_MSG_CHECKING([for $1 options with pkg-config])