[wasm] configure.ac: setup platform specific libraries

These flags are very wasi-libc version specific, so updating wasi-libc
may break the build. But supporting multiple wasi-libc versions in ruby
doesn't have much benefit because wasi-libc is not installed in most
systems.

configure.ac

@@ -1215,6 +1215,10 @@ main()
 		RUBY_APPEND_OPTIONS(LDFLAGS, "-sFORCE_FILESYSTEM=1")
 		ac_cv_func_shutdown=no
 		],
+[wasi*],[	LIBS="-lm -lwasi-emulated-mman -lwasi-emulated-signal -lwasi-emulated-getpid -lwasi-emulated-process-clocks $LIBS"
+		RUBY_APPEND_OPTIONS(CFLAGS, -D_WASI_EMULATED_SIGNAL -D_WASI_EMULATED_MMAN -D_WASI_EMULATED_GETPID -D_WASI_EMULATED_PROCESS_CLOCKS)
+		RUBY_APPEND_OPTIONS(CPPFLAGS, -D_WASI_EMULATED_SIGNAL -D_WASI_EMULATED_MMAN -D_WASI_EMULATED_GETPID -D_WASI_EMULATED_PROCESS_CLOCKS)
+		]
 [	LIBS="-lm $LIBS"])
 : ${ORIG_LIBS=$LIBS}