mythmusic: Fix cross compiling for win32

When cross compiling for win32, mythplugins configure fails to find a
number of required libraries for mythmusic, which is then disabled.

This patch adds the correct library search paths and additional libs.

NB to correctly run configure for mythmusic on mingw requires an updated
mythbuild.sh.

Fixes #10742

Signed-off-by: Lawrence Rust <lvr@softsystem.co.uk>
Signed-off-by: Gavin Hurlbut <ghurlbut@mythtv.org>

mythplugins/configure

@@ -151,7 +151,7 @@ check_ld(){
         test "${f}" = "${f#-l}" && flags="$flags $f" || libs="$libs $f"
     done
     check_cc $($filter_cflags $flags) || return
-    check_cmd $LD $LDFLAGS $flags -o $TMPE $TMPO $libs
+    check_cmd $LD $LDFLAGS $flags -o $TMPE $TMPO $libs $EXTRALIBS
 }
 
 check_header(){
@@ -555,6 +555,9 @@ CXXPPFLAGS=$(cat mythconfig.mak | grep -e "^CXXPPFLAGS=")
 CXXPPFLAGS=${CXXPPFLAGS#CXXPPFLAGS=}
 OPENGLV=$(cat mythconfig.mak | grep -e "^CONFIG_OPENGL_VIDEO=yes")
 
+EXTRALIBS=$(cat mythconfig.mak | grep -e "^EXTRALIBS=")
+EXTRALIBS=${EXTRALIBS#EXTRALIBS=}
+
 if ! is_qmake4 $qmake; then
     is_qmake4 qmake-qt4 && qmake=qmake-qt4 || die "qmake for Qt4.6 or newer not found.\nPlease specify the correct qmake with --qmake="
 fi