Fix bugs with unicode filenames in runfiles.

We had a cc_test using a bunch of files (`data = glob(["data/**"]),`), some which were in subdirectories where the directory name had unicode characters (e.g. `data/test_öΩ/`).
This resulted in an error:
```
ERROR: C:/users/.../BUILD.bazel:233:8: Creating runfiles tree bazel-out/x64_windows-opt/test-shared.exe.runfiles failed: build-runfiles.exe failed: error executing command
  cd /d C:\users\...
  SET BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN=1
    SET PATH=...
  C:\users\...\install\eadbc20bd36081cbe58dcb5129383507\build-runfiles.exe bazel-out/x64_windows-opt/test-shared.exe.runfiles_manifest bazel-out/x64_windows-opt/test-shared.exe.runfiles: Process exited with status 1: Process exited with status 1
build-runfiles error: MakeDirectoriesW failed (\\?\c:\users\...\test-shared.exe.runfiles\test\data\layer_middle_??): (error: 123): The filename, directory name, or volume label syntax is incorrect.
```

`build-runfiles-windows.cc` expects the `.runfiles_manifest` to be encoded in UTF-8; but Java was writing it as latin-1. This resulted in unicode characters (not representable in latin-1) being stored as `?` in the `.runfiles_manifest` file. Question marks are not valid in filenames, causing the error in `build-runfiles`.

This commit changes the encoding of `.runfiles_manifest` from latin-1 to UTF-8. Additionally, it fixes a bug in `build-runfiles-windows.cc` where the `space_pos` was calculated from the UTF-8 representation but then used for the UTF-16 wstring, which caused string containing unicode characters to be split incorrectly.

Closes #15846.

PiperOrigin-RevId: 509492501
Change-Id: I82d5119160c16d4513e9e744d9f398727bac1dc4

src/main/java/com/google/devtools/build/lib/analysis/SourceManifestAction.java

@@ -14,7 +14,6 @@
 package com.google.devtools.build.lib.analysis;
 
 import static com.google.common.collect.ImmutableList.toImmutableList;
-import static java.nio.charset.StandardCharsets.ISO_8859_1;
 import static java.nio.charset.StandardCharsets.UTF_8;
 
 import com.google.common.annotations.VisibleForTesting;
@@ -225,7 +224,7 @@ public boolean isRemotable() {
    * @throws IOException
    */
   private void writeFile(OutputStream out, Map<PathFragment, Artifact> output) throws IOException {
-    Writer manifestFile = new BufferedWriter(new OutputStreamWriter(out, ISO_8859_1));
+    Writer manifestFile = new BufferedWriter(new OutputStreamWriter(out, UTF_8));
     List<Map.Entry<PathFragment, Artifact>> sortedManifest = new ArrayList<>(output.entrySet());
     sortedManifest.sort(ENTRY_COMPARATOR);
     for (Map.Entry<PathFragment, Artifact> line : sortedManifest) {

src/main/tools/build-runfiles-windows.cc

@@ -164,8 +164,8 @@ class RunfilesCreator {
         continue;
       }
 
-      size_t space_pos = line.find_first_of(' ');
       wstring wline = blaze_util::CstringToWstring(line);
+      size_t space_pos = wline.find_first_of(' ');
       wstring link, target;
       if (space_pos == string::npos) {
         link = wline;