…ailable.

So that you can set a `--spawn_strategy` that includes `remote` without setting `--remote_executor`. In addition, if `--remote_local_fallback` is set and `remote_executor` is unreachable when build starts, Bazel will fallback to next available strategy.

Fixes bazelbuild#13340 and bazelbuild#13487.

Closes bazelbuild#13490.

PiperOrigin-RevId: 378339904

…ailable.

So that you can set a `--spawn_strategy` that includes `remote` without setting `--remote_executor`. In addition, if `--remote_local_fallback` is set and `remote_executor` is unreachable when build starts, Bazel will fallback to next available strategy.

Fixes bazelbuild#13340 and bazelbuild#13487.

Closes bazelbuild#13490.

PiperOrigin-RevId: 378339904

…ailable.

So that you can set a `--spawn_strategy` that includes `remote` without setting `--remote_executor`. In addition, if `--remote_local_fallback` is set and `remote_executor` is unreachable when build starts, Bazel will fallback to next available strategy.

Fixes bazelbuild#13340 and bazelbuild#13487.

Closes bazelbuild#13490.

PiperOrigin-RevId: 378339904

…ailable.

So that you can set a `--spawn_strategy` that includes `remote` without setting `--remote_executor`. In addition, if `--remote_local_fallback` is set and `remote_executor` is unreachable when build starts, Bazel will fallback to next available strategy.

Fixes bazelbuild#13340 and bazelbuild#13487.

Closes bazelbuild#13490.

PiperOrigin-RevId: 378339904

…ailable.

So that you can set a `--spawn_strategy` that includes `remote` without setting `--remote_executor`. In addition, if `--remote_local_fallback` is set and `remote_executor` is unreachable when build starts, Bazel will fallback to next available strategy.

Fixes bazelbuild#13340 and bazelbuild#13487.

Closes bazelbuild#13490.

PiperOrigin-RevId: 378339904

…7945)

### What does this PR do?
Adjust the `cache` Bazel config following a complete review of the remote flags:
1. switch `--remote_executor` to `--remote_cache` since RBE infrastructure is not ready,
2. add `--incompatible_remote_local_fallback_for_remote_cache` to enable local fallback on remote cache failures,
3. remove `--remote_local_fallback_strategy=sandboxed` from the `linux` and `macos` configs, which became dead letter.

### Motivation
[Earlier discussion](https://dd.slack.com/archives/C08SK4B0FK8/p1773737357223759).

#### 1. `--remote_executor` to `--remote_cache`
The build farm is used as a remote cache, not a remote executor.
[Quoting](#47945 (comment)) @JSGette, who filed bazelbuild/bazel#29129:
> fallback is basically broken for remote executor if an endpoint is unavailable **before** the build. So if buildbarn was to fail **during** the build Bazel would just continue locally.

#### 2. `--incompatible_remote_local_fallback_for_remote_cache`
The flag was introduced with Bazel 8.5.1 (bazelbuild/bazel#27996) since `--remote_local_fallback` alone does not cover cache-layer failures.
Both flags are required because [they are AND-gated at the single decision point](https://github.com/bazelbuild/bazel/blob/9.0.1/src/main/java/com/google/devtools/build/lib/remote/RemoteSpawnCache.java#L191):
```java
          boolean shouldLocalFallback =
              options.remoteLocalFallbackForRemoteCache && options.remoteLocalFallback;
```
Without **both** flags, a `RemoteExecutionCapabilitiesException` (capabilities fetch failure) causes a hard build failure instead of a local fallback.

#### 3. `--remote_local_fallback_strategy` removal
The flag is unreachable in a `--remote_cache`-only setup: its single call site is `RemoteSpawnRunner.execLocally()`, gated by `RemoteExecutionService.mayBeExecutedRemotely()`, which requires `remoteExecutor != null`.
It is also `@Deprecated` (bazelbuild/bazel#7480).

### Describe how you validated your changes
The flag is a no-op outside `--config=cache` (local builds unaffected by default), but CI benefits from it by default.

### Additional Notes
The stale `registerRemoteSpawnStrategy()` javadoc (["otherwise does nothing"](https://github.com/bazelbuild/bazel/blob/9.0.1/src/main/java/com/google/devtools/build/lib/remote/RemoteActionContextProvider.java#L195-L196) when no executor is set) is a known source-reading hazard: the null-check was deliberately removed in bazelbuild/bazel#13490 (2021), moving the guard to `canExec()`.
The javadoc was never updated.

Co-authored-by: regis.desgroppes <[email protected]>