archivers/upx: Fix build on 14-CURRENT

In file included from filteri.cpp:71:
./filter/cto.h:47:39: error: variable 'noncalls2' set but not used [-Werror,-Wunused-but-set-variable]
    unsigned calls = 0, noncalls = 0, noncalls2 = 0;
                                      ^
In file included from filteri.cpp:73:
./filter/cto.h:47:39: error: variable 'noncalls2' set but not used [-Werror,-Wunused-but-set-variable]
    unsigned calls = 0, noncalls = 0, noncalls2 = 0;
                                      ^
In file included from filteri.cpp:79:
./filter/cto.h:47:39: error: variable 'noncalls2' set but not used [-Werror,-Wunused-but-set-variable]
    unsigned calls = 0, noncalls = 0, noncalls2 = 0;
                                      ^
In file included from filteri.cpp:81:
./filter/cto.h:47:39: error: variable 'noncalls2' set but not used [-Werror,-Wunused-but-set-variable]
    unsigned calls = 0, noncalls = 0, noncalls2 = 0;
                                      ^
In file included from filteri.cpp:87:
./filter/cto.h:47:39: error: variable 'noncalls2' set but not used [-Werror,-Wunused-but-set-variable]
    unsigned calls = 0, noncalls = 0, noncalls2 = 0;
                                      ^
In file included from filteri.cpp:89:
./filter/cto.h:47:39: error: variable 'noncalls2' set but not used [-Werror,-Wunused-but-set-variable]
    unsigned calls = 0, noncalls = 0, noncalls2 = 0;
                                      ^
In file included from filteri.cpp:100:
./filter/ctoj.h:51:39: error: variable 'noncalls2' set but not used [-Werror,-Wunused-but-set-variable]
    unsigned calls = 0, noncalls = 0, noncalls2 = 0;
                                      ^
In file included from filteri.cpp:102:
./filter/ctoj.h:51:39: error: variable 'noncalls2' set but not used [-Werror,-Wunused-but-set-variable]
    unsigned calls = 0, noncalls = 0, noncalls2 = 0;
                                      ^
In file included from filteri.cpp:115:
./filter/ctok.h:52:39: error: variable 'noncalls2' set but not used [-Werror,-Wunused-but-set-variable]
    unsigned calls = 0, noncalls = 0, noncalls2 = 0;
                                      ^
In file included from filteri.cpp:117:
./filter/ctok.h:52:39: error: variable 'noncalls2' set but not used [-Werror,-Wunused-but-set-variable]
    unsigned calls = 0, noncalls = 0, noncalls2 = 0;
                                      ^
In file included from filteri.cpp:141:
./filter/ctojr.h:109:39: error: variable 'noncalls2' set but not used [-Werror,-Wunused-but-set-variable]
    unsigned calls = 0, noncalls = 0, noncalls2 = 0;
                                      ^
In file included from filteri.cpp:143:
./filter/ctojr.h:109:39: error: variable 'noncalls2' set but not used [-Werror,-Wunused-but-set-variable]
    unsigned calls = 0, noncalls = 0, noncalls2 = 0;
                                      ^
12 errors generated.

Reference:	https://pkg-status.freebsd.org/beefy18/data/main-amd64-default/pdf5b273c8e36_s83d5725005/logs/upx-3.96.log

archivers/upx/Makefile

@@ -24,8 +24,14 @@ PLIST_FILES=	bin/upx \
 
 CPE_VENDOR=	upx_project
 
+.include <bsd.port.pre.mk>
+
+.if ${OPSYS} == FreeBSD && ${OSVERSION} >= 1400079
+CFLAGS+=       -Wno-error=unused-but-set-variable
+.endif
+
 do-install:
 	${INSTALL_PROGRAM} ${WRKSRC}/src/upx.out ${STAGEDIR}${PREFIX}/bin/upx
 	${INSTALL_MAN} ${WRKSRC}/doc/upx.1 ${STAGEDIR}${PREFIX}/man/man1
 
-.include <bsd.port.mk>
+.include <bsd.port.post.mk>