Use -lxxx internally rather than full library path (#14342)

Since we already supply the correct `-L` path we can rely on wasm-ld to
find, for example, libc.a by simply pasing `-lc` rather than its full
path.

This is in line with what gcc and clang do.

This is almost NFC, except in that case where the user supplies and
library path via `-L` which happens to contains a file called `libc.a`.
In this case, as with clang or gcc, that file will be chosen over the
system one.

This makes the linker command lines shorter, more readable, more in line
with other compilers.

Author: sbc100

ChangeLog.md

@@ -21,6 +21,12 @@ See docs/process.md for more on how version tagging works.
 2.0.24
 ------
 - Support `--preload-file` in Node.js. (#11785)
+- System libraries are now passed to the linker internally via `-lfoo` rather
+  than using their full path.  This is in line with how gcc and clang pass system
+  libraries to the linker.  This should not effect any builds unless a project a
+  happens to have, for example, a file called `libc.a` in one of its library
+  paths.  This would have the effect of overriding the system library (as it
+  would with gcc or clang) (#14342).
 - CMake projects (those that either use emcmake or use Emscripten.cmake
   directly) are new configured to install (by default) directly into the
   emscripten sysroot.  This means that running `cmake --install` (or running the

tools/system_libs.py

@@ -300,6 +300,20 @@ def get_path(self):
     """
     return shared.Cache.get_lib(self.get_filename(), self.build)
 
+  def get_link_flag(self):
+    """
+    Gets the link flags needed to use the library.
+
+    This will trigger a build if this library is not in the cache.
+    """
+    fullpath = self.get_path()
+    # For non-libaries (e.g. crt1.o) we pass the entire path to the linker
+    if self.get_ext() != '.a':
+      return fullpath
+    # For libraries (.a) files, we pass the abbreviated `-l` form.
+    base = shared.unsuffixed_basename(fullpath)
+    return '-l' + shared.strip_prefix(base, 'lib')
+
   def get_files(self):
     """
     Gets a list of source files for this library.
@@ -1487,7 +1501,7 @@ def add_library(libname):
     logger.debug('including %s (%s)' % (lib.name, lib.get_filename()))
 
     need_whole_archive = lib.name in force_include and lib.get_ext() == '.a'
-    libs_to_link.append((lib.get_path(), need_whole_archive))
+    libs_to_link.append((lib.get_link_flag(), need_whole_archive))
 
   if settings.USE_PTHREADS:
     add_library('crtbegin')