The problem here is that libgambatte and gambatte_sdl are separate projects, if you read scons(1) you'll see that the -C operand doesn't work the way that you intended.
The following seems to work.. and it's a little cleaner, but please considering posting to the list for further critiquing from qualified eyes.
Code:
--- Makefile.orig Mon Sep 7 23:50:01 2009
+++ Makefile Mon Sep 7 23:48:26 2009
@@ -20,13 +20,14 @@
LIB_DEPENDS += SDL::devel/sdl
WANTLIB += c m pthread stdc++ z
+WRKSRC=${WRKDIST}/gambatte_sdl
+
do-build:
- @${SETENV} ${MAKE_ENV} ${MODSCONS_BIN} -C ${WRKSRC}/gambatte_sdl \
- -C ${WRKSRC}/libgambatte
+ ${MODSCONS_BIN} -C ${WRKDIST}/libgambatte
+ ${MODSCONS_BIN} -C ${WRKSRC}
do-install:
- ${INSTALL_PROGRAM} ${WRKBUILD}/gambatte_sdl/gambatte_sdl ${PREFIX}/bin/
- ${INSTALL_MAN} ${WRKBUILD}/gambatte_sdl/man/gambatte_sdl.6 \
- ${PREFIX}/man/man6/
+ ${INSTALL_PROGRAM} ${WRKSRC}/gambatte_sdl ${PREFIX}/bin
+ ${INSTALL_MAN} ${WRKSRC}/man/gambatte_sdl.6 ${PREFIX}/man/man6
.include <bsd.port.mk>
Hope that helps.