configure.ac: Drop no longer needed SP_PKGLIBS.

configure.ac

@@ -75,10 +75,6 @@ AC_SUBST(SP_LIB_LDFLAGS)
 
 # Checks for libraries.
 
-# This variable collects the pkg-config names of all detected libs.
-# It is then used to construct the "Requires.private:" field in the
-# libserialport.pc file.
-SP_PKGLIBS=""
 SP_LIBS=""
 
 case $host_os in
@@ -118,7 +114,6 @@ mingw* | cygwin*)
 	AC_DEFINE(NO_PORT_METADATA,,[Port metadata is unavailable])
 esac
 
-AC_SUBST(SP_PKGLIBS)
 AC_SUBST(SP_LIBS)
 
 # Define size_t if not defined as standard.

libserialport.pc.in

@@ -6,7 +6,7 @@ includedir=@includedir@
 Name: libserialport
 Description: Cross-platform serial port access library.
 URL: http://sigrok.org/wiki/Libserialport
-Requires.private: @SP_PKGLIBS@
+Requires.private:
 Version: @VERSION@
 Libs: -L${libdir} -lserialport
 Libs.private: @SP_LIBS@