misc/cuttlefish: fix build on armv7

Tell clang that it's ok to use fp16 instructions as the port assumes the
corresponding intrinsics are present.

Approved by:	portmgr (build fix blanket)
MFH:		2023Q3

misc/cuttlefish/Makefile

@@ -32,6 +32,7 @@ CMAKE_OFF=	CUTTLEFISH_BUILD_DOCS CUTTLEFISH_BUILD_TESTS
 CMAKE_ON=	CUTTLEFISH_SHARED
 CMAKE_TESTING_ON=	CUTTLEFISH_BUILD_TESTS # many tests fail, see https://github.com/akb825/Cuttlefish/issues/19
 
+CXXFLAGS_armv7=	-mfpu=neon-fp16
 CXXFLAGS_powerpc=	-maltivec
 
 .include <bsd.port.mk>