WasmFS: Do not link in the no-fs version when forced-fs [NFC] (#19563)

I don't think this fixes any actual bug - it should just be wasted work that this PR
avoids - but it was confusing to me to even see it on the link command, when it
obviously should not be there (when the FS is forced, we must include it, and not
the no-fs version).

Author: kripken

tools/system_libs.py

@@ -1878,7 +1878,8 @@ class libwasmfs_no_fs(Library):
   src_files = ['no_fs.c']
 
   def can_use(self):
-    return settings.WASMFS
+    # If the filesystem is forced then we definitely do not need this library.
+    return settings.WASMFS and not settings.FORCE_FILESYSTEM
 
 
 class libwasmfs_noderawfs(Library):
@@ -2217,8 +2218,12 @@ def add_sanitizer_libs():
 
   if settings.WASMFS:
     # Link in the no-fs version first, so that if it provides all the needed
-    # system libraries then WasmFS is not linked in at all.
-    add_library('libwasmfs_no_fs')
+    # system libraries then WasmFS is not linked in at all. (We only do this if
+    # the filesystem is not forced; if it is then we know we definitely need the
+    # whole thing, and it would be unnecessary work to try to link in the no-fs
+    # version).
+    if not settings.FORCE_FILESYSTEM:
+      add_library('libwasmfs_no_fs')
     add_library('libwasmfs')
 
   add_sanitizer_libs()