graphics/pgplot: Fix building with Flang

graphics/pgplot/Makefile

@@ -24,8 +24,8 @@ MAKE_JOBS_UNSAFE=	yes
 
 MAKE_ENV=	SSP_CFLAGS=
 SHEBANG_FILES=	makehtml maketex
-FFLAGS+=	-std=legacy
 SUFFIXES=	flib clib bin
+CFLAGS=		-Wno-implicit-function-declaration
 WRKSRC=		${WRKDIR}/${PORTNAME}
 
 # ld.bfd supports neither -z relro nor -z norelro on armv7
@@ -56,6 +56,12 @@ EXAMPLES=	Makefile.demo cpg/cpgdemo.c examples/pgdemo*.f
 PORTEXAMPLES=	${EXAMPLES:C|.*/||}
 .endif
 
+.include <bsd.port.pre.mk>
+
+.if ${FORTRAN_DEFAULT} == gfortran
+FFLAGS+=	-std=legacy
+.endif
+
 post-patch:
 	@${REINPLACE_CMD} -e 's|png_ptr->jmpbuf|png_jmpbuf(png_ptr)|' \
 		${WRKSRC}/drivers/pndriv.c
@@ -102,4 +108,4 @@ check test: build
 	PGPLOT_DIR="${WRKSRC}" PGPLOT_DEV="/xwin" ${WRKSRC}/${DEMO}
 .endif
 
-.include <bsd.port.mk>
+.include <bsd.port.post.mk>