Install working pkgconfig .pc files for compat libraries

The default ones are install them to /usr/libdata/pkgconfig, and we can't
use this path for compat libraries, so we use /usr/lib<suffix>/pkgconfigi here.

Test Plan:	grep -rn libdir= ./usr/lib32/pkgconfig/*.pc
MFC after:	1 week
Differential Revision: https://reviews.freebsd.org/D34939

lib/libusb/Makefile

@@ -35,6 +35,12 @@ SRCS+=		libusb10_hotplug.c
 SRCS+=		libusb10_io.c
 
 PCFILES=	libusb-0.1.pc libusb-1.0.pc libusb-2.0.pc
+.for pcfile in ${PCFILES}
+${pcfile}: ${pcfile}.in
+	sed -e 's,@libdir@,${LIBDIR},g ; s,@sharedlibdir@,${SHLIBDIR},g ; \
+		s,@includedir@,${INCLUDEDIR},g ;' ${.ALLSRC} > ${.TARGET}
+.endfor
+CLEANFILES+=	${PCFILES}
 
 #
 # Cross platform support

lib/libusb/libusb-0.1.pc.in

@@ -1,8 +1,9 @@
 # $FreeBSD$
 prefix=/usr
 exec_prefix=${prefix}
-libdir=${exec_prefix}/lib
-includedir=${prefix}/include
+libdir=@libdir@
+sharedlibdir=@sharedlibdir@
+includedir=@includedir@
 
 Name: libusb-0.1
 Description: Library that abstracts ways to access USB devices (v0.1)

lib/libusb/libusb-1.0.pc.in

@@ -1,8 +1,9 @@
 # $FreeBSD$
 prefix=/usr
 exec_prefix=${prefix}
-libdir=${exec_prefix}/lib
-includedir=${prefix}/include
+libdir=@libdir@
+sharedlibdir=@sharedlibdir@
+includedir=@includedir@
 
 Name: libusb-1.0
 Description: Library that abstracts ways to access USB devices (v1.0)

lib/libusb/libusb-2.0.pc.in

@@ -1,8 +1,9 @@
 # $FreeBSD$
 prefix=/usr
 exec_prefix=${prefix}
-libdir=${exec_prefix}/lib
-includedir=${prefix}/include
+libdir=@libdir@
+sharedlibdir=@sharedlibdir@
+includedir=@includedir@
 
 Name: libusb-2.0
 Description: Library that abstracts ways to access USB devices (v2.0)