lang/gforth: attempt to unbreak the port on i386, armv6, and armv7

• Partially apply upstream commit 9f35279358 to unbreak the build on i386
• With a recent update of devel/libffcall in 58a8a0aa37a8, the port is no longer ignored on armv6 and armv7. Amend the word size check so it can be built on these architectures

PR: 258003