Fix a typo with the libtool flag -export-symbols-regex

Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>
(cherry picked from commit 3a27eb58)

modules/common.am

@@ -19,7 +19,7 @@ AM_CXXFLAGS = `$(VLC_CONFIG) --cxxflags plugin $@`
 AM_OBJCFLAGS = `$(VLC_CONFIG) --objcflags plugin $@`
 AM_LDFLAGS = -rpath '$(libvlcdir)' \
 	-avoid-version -module \
-	-export-symbol-regex ^vlc_entry \
+	-export-symbols-regex ^vlc_entry \
 	-shrext $(LIBEXT) \
 	-rpath "$(libvlcdir)" \
 	-no-undefined \