Include dependency libs (-lm) in the pkg-config file

configure.ac

@@ -27,7 +27,11 @@ dnl soname version to use
 dnl goes by ‘current[:revision[:age]]’ with the soname ending up as
 dnl current.age.revision
 FDK_AAC_VERSION=0:2:0
+
+AS_IF([test x$enable_shared = xyes], [LIBS_PRIVATE=$LIBS], [LIBS_PUBLIC=$LIBS])
 AC_SUBST(FDK_AAC_VERSION)
+AC_SUBST(LIBS_PUBLIC)
+AC_SUBST(LIBS_PRIVATE)
 
 AC_CONFIG_FILES([Makefile
                  fdk-aac.pc])

fdk-aac.pc.in

@@ -6,5 +6,6 @@ includedir=@includedir@
 Name: Fraunhofer FDK AAC Codec Library
 Description: AAC codec library
 Version: @PACKAGE_VERSION@
-Libs: -L${libdir} -lfdk-aac
+Libs: -L${libdir} -lfdk-aac @LIBS_PUBLIC@
+Libs.private: @LIBS_PRIVATE@
 Cflags: -I${includedir}