Disable use of build system pkg-config files when cross-compiling

Using build system libraries for a different host doesn't make sense and
can be actively harmful, so set PKG_CONFIG_LIBDIR to prevent pkg-config
from finding them (it, or PKG_CONFIG_PATH, can still be set to some
host-appropriate directory manually before/when running configure).

This obviates the need for the changes in the previous commit, so revert
it.

configure

@@ -21642,6 +21642,15 @@ $as_echo "no" >&6; }
 
 fi
 
+if test "$build" != "$host"; then
+
+
+                if test -z "$PKG_CONFIG_LIBDIR"; then
+        PKG_CONFIG_LIBDIR=/dev/null
+        export PKG_CONFIG_LIBDIR
+    fi
+fi
+
 
 
 if test "$wxUSE_REGEX" != "no"; then
@@ -23004,8 +23013,6 @@ if test "$wxUSE_LIBMSPACK" != "no"; then
 fi
 
 
-if test "$wxUSE_OSX_IPHONE" != 1; then
-
 if test "$wxUSE_LIBCURL" != "no"; then
 
 pkg_failed=no
@@ -23101,7 +23108,6 @@ $as_echo "$as_me: WARNING: libcurl not found, wxWebRequest won't be available" >
     fi
 fi
 
-fi
 
 TOOLKIT=
 TOOLKIT_INCLUDE=