Build fixes for libepoll-shim

- correct compiler flags when using GCC; clears BROKEN on PPC64
- correct spelling of INCSDIR; fixes build when PREFIX != /usr/local [1]

PR:		219576 [1]
Submitted by:	John Hein [1]
Reported by:	Mikhail T. [1]
Approved by:	swills (mentor)
Differential Revision:	https://reviews.freebsd.org/D11551

devel/libepoll-shim/Makefile

@@ -10,8 +10,6 @@ COMMENT=	epoll shim implemented using kevent
 
 LICENSE=	MIT
 
-BROKEN_powerpc64=	fails to compile: cc1: error: unrecognized command line option -Wno-missing-variable-declarations
-
 USE_GITHUB=	yes
 GH_ACCOUNT=	FreeBSDDesktop
 GH_PROJECT=	epoll-shim
@@ -19,14 +17,18 @@ GH_TAGNAME=	c04b26b
 
 USE_LDCONFIG=	yes
 
-USES=		uidfix
-MAKE_ARGS=	LIBDIR=${PREFIX}/lib INCLUDEDIR=${PREFIX}/include
+USES=		compiler uidfix
+MAKE_ARGS=	LIBDIR=${PREFIX}/lib INCSDIR=${PREFIX}/include/libepoll-shim/sys
+
+.include <bsd.port.pre.mk>
 
 post-patch:
-	# -Weverything is not recognized by GCC
-	@${REINPLACE_CMD} -e 's|Weverything|Wall|' ${WRKSRC}/Makefile
+.if "${CHOSEN_COMPILER_TYPE}" == "gcc"
+	@${REINPLACE_CMD} -e 's|Wno-missing-variable-declarations|Wno-missing-declarations|' \
+		-e 's|-Wno-thread-safety-analysis||' -e 's|Weverything|Wall|' ${WRKSRC}/Makefile
+.endif
 
 pre-install:
 	@${MKDIR} ${STAGEDIR}/${PREFIX}/include/libepoll-shim/sys
 
-.include <bsd.port.mk>
+.include <bsd.port.post.mk>