configure: move ranlib -D test after setting defaults

In Gentoo and ChromeOS we want to allow pure LLVM builds without
using GNU tools, so we block any unwanted mixed GNU/LLVM usages
(GNU tools are still kept around in our chroots for projects
like glibc which cannot yet be built otherwise).

The default ${cross_prefix}${ranlib_default} points to GNU and
fails, so move the test a bit later - after the defaults are
set and the proper values get overriden - such that ffmpeg
configure calls the llvm-ranlib we desire. [1]

[1] https://gitweb.gentoo.org/repo/gentoo.git/tree/media-video/ffmpeg/ffmpeg-4.4.1-r1.ebuild?id=7a34377e3277a6a0e2eedd40e90452a44c55f1e6#n477

Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com>
Signed-off-by: Martin Storsjö <martin@martin.st>

configure

@@ -4403,11 +4403,7 @@ cc_default="${cross_prefix}${cc_default}"
 cxx_default="${cross_prefix}${cxx_default}"
 nm_default="${cross_prefix}${nm_default}"
 pkg_config_default="${cross_prefix}${pkg_config_default}"
-if ${cross_prefix}${ranlib_default} 2>&1 | grep -q "\-D "; then
-    ranlib_default="${cross_prefix}${ranlib_default} -D"
-else
-    ranlib_default="${cross_prefix}${ranlib_default}"
-fi
+ranlib_default="${cross_prefix}${ranlib_default}"
 strip_default="${cross_prefix}${strip_default}"
 windres_default="${cross_prefix}${windres_default}"
 
@@ -4440,6 +4436,10 @@ set_default arch cc cxx doxygen pkg_config ranlib strip sysinclude \
 enabled cross_compile || host_cc_default=$cc
 set_default host_cc
 
+if ${ranlib} 2>&1 | grep -q "\-D "; then
+    ranlib="${ranlib} -D"
+fi
+
 pkg_config_fail_message=""
 if ! $pkg_config --version >/dev/null 2>&1; then
     warn "$pkg_config not found, library detection may fail."