Fix / suppress warnings for clang+mingw

Switch attribute error to attribute unavailable, which apparently works
since it then broke the build :-/

Suppress unused parameter warnings. They aren't that useful for windows
functions that are just #ifndef WIN32. This is marked as a global cflag,
but something is overriding that with the clang+mingw changes, and it's
not actually that hard to suppress or fix where necessary.

Bug: 69933068
Test: mmma build/tools/libhost
Change-Id: I09adda4544bc9b56452b4fe182dba3d0b701dcbb

tools/libhost/Android.bp

@@ -10,6 +10,7 @@ cc_library_host_static {
     name: "libhost",
     target: {
         windows: {
+            cflags: ["-Wno-unused-parameter"],
             enabled: true,
         },
     },

tools/libhost/CopyFile.c

@@ -352,7 +352,12 @@ static int copyRegular(const char* src, const char* dst, const struct stat* pSrc
  * need to trash it so we can create one.
  */
 #if defined(_WIN32)
-extern int copySymlink(const char* src, const char* dst, const struct stat* pSrcStat, unsigned int options) __attribute__((error("no symlinks on Windows")));
+extern int copySymlink(const char* src, const char* dst, const struct stat* pSrcStat, unsigned int options)
+#ifdef __clang__
+  __attribute__((unavailable("no symlinks on Windows")));
+#else
+  __attribute__((error("no symlinks on Windows")));
+#endif
 #else
 static int copySymlink(const char* src, const char* dst, const struct stat* pSrcStat, unsigned int options)
 {
@@ -574,8 +579,10 @@ static int copyFileRecursive(const char* src, const char* dst, bool isCmdLine, u
         } else {
             retVal = copyDirectory(src, dst, &srcStat, options);
         }
+#if !defined(_WIN32)
     } else if (S_ISLNK(srcStat.st_mode)) {
         retVal = copySymlink(src, dst, &srcStat, options);
+#endif
     } else if (S_ISREG(srcStat.st_mode)) {
         retVal = copyRegular(src, dst, &srcStat, options);
     } else {