Fix CI diagnostics for failed bazel builds on Windows (#42006)

### What does this PR do?
CI diagnostics for failed `bazel` builds on Windows didn't work as
expected (see #41844 for more details).

The change consists in:
- removing the pseudo-shebang that was preventing from resolving paths
relative to the source script's location,
- making sure the output is UTF-8 (`chcp 65001`) to echo non-ASCII
characters from dumped contents,
- using the right `bazel` startup flag (`--local_startup_timeout_secs`)
to limit the total retry loop to 30s,
while making the retries more frequent (`--connect_timeout_secs`) inside
the loop,
- no longer assuming `$CI_PROJECT_DIR` resolves to the workspace's root,
- payload: fixing/discovering base location for server logs which happen
to be under a subdirectory whose name is a hash (`jgkidtko` on my VM).

### Motivation
Really get actionable outputs for addressing `FATAL: couldn't connect to
server` errors.

### Describe how you validated your changes
Reproduced CI layout locally and fixed the script to make it provide
with available info on `bazel` build failures.

### Additional Notes
This is of course temporary until we figure out what's preventing the
`bazel` CLI from contacting the server.

Author: rdesgroppes

tools/bazel.bat

@@ -1,6 +1,5 @@
-@echo off & setlocal EnableDelayedExpansion & if not defined bb (set "bb=%TEMP%\%~n0-%RANDOM%.bat" & more /e /p "%~f0" >"!bb!" & call "!bb!" %* & set "rc=!errorlevel!" & del /q "!bb!" & exit /b !rc!)
-:: Above one-liner copies the present script to a temporary file with normalized Windows line endings and executes it.
-:: Works regardless of actual source line endings because the pseudo-shebang is interpreted before the first newline.
+@echo off & setlocal EnableDelayedExpansion
+>nul chcp 65001
 
 :: Check `bazelisk` properly bootstraps `bazel` or fail with instructions
 if not defined BAZEL_REAL (
@@ -41,12 +40,13 @@ if exist "!BAZEL_REPO_CONTENTS_CACHE!" (
 
 :: Pass CI-specific options through `.user.bazelrc` so any nested `bazel run` and next `bazel shutdown` also honor them
 (
-  echo startup --connect_timeout_secs=30
+  echo startup --connect_timeout_secs=5  # instead of 30s, for quicker iterations in diagnostics
+  echo startup --local_startup_timeout_secs=30  # instead of 120s, to fail faster for diagnostics
   echo startup --output_user_root=!BAZEL_OUTPUT_USER_ROOT!
   echo common --config=cache
   echo common --repo_contents_cache=!ext_repo_contents_cache!
   echo build --disk_cache=!BAZEL_DISK_CACHE!
-) >"%CI_PROJECT_DIR%\user.bazelrc"
+) >"%~dp0..\user.bazelrc"
 
 :: Diagnostics: print any stalled client/server before `bazel` execution
 >&2 powershell -NoProfile -Command "Get-Process bazel,java -ErrorAction SilentlyContinue | Select-Object 🟡,ProcessName,StartTime"
@@ -55,16 +55,22 @@ if exist "!BAZEL_REPO_CONTENTS_CACHE!" (
 "%BAZEL_REAL%" %*
 set "bazel_exit=!errorlevel!"
 
-:: Diagnostics: dump JVM output on failure
+:: Diagnostics: dump logs on failure
 if !bazel_exit! neq 0 (
-  >&2 echo 🟡 JVM output:
-  >&2 type "!BAZEL_OUTPUT_USER_ROOT!\server\jvm.out"
+  >&2 echo 🟡 Bazel failed, dumping available info:
+  for /d %%d in ("!BAZEL_OUTPUT_USER_ROOT!\*") do (
+    for %%f in ("%%d\java.log.*" "%%d\server\*") do (
+      >&2 echo 🟡 %%f:
+      >&2 type "%%f"
+      >&2 echo.
+    )
+  )
   exit /b !bazel_exit!
 )
 
 :: Stop `bazel` (if still running) to close files and proceed with cleanup
 >&2 "%BAZEL_REAL%" shutdown --ui_event_filters=-info
->&2 del /f /q "%CI_PROJECT_DIR%\user.bazelrc"
+>&2 del /f /q "%~dp0..\user.bazelrc"
 
 :: Reintegrate `--repo_contents_cache` to original directory
 if exist "!ext_repo_contents_cache!" (