devel/libepoll-shim would not build with non-default PREFIX

[Mikhail T.]

The following patch is necessary -- the currently-used INCLUDEDIR
knob has no effect:

Index: Makefile
===================================================================
--- Makefile	(revision 444886)
+++ Makefile	(working copy)
@@ -20,7 +20,7 @@
 USE_LDCONFIG=	yes
 
 USES=		uidfix
-MAKE_ARGS=	LIBDIR=${PREFIX}/lib INCLUDEDIR=${PREFIX}/include
+MAKE_ARGS=	LIBDIR=${PREFIX}/lib INCSDIR=${PREFIX}/include/libepoll-shim/sys
 
 post-patch:
 	# -Weverything is not recognized by GCC

	-mi (mi at aldan.algebra.com)