Disable USE_RBE with b builds (m bp2build).

RBE is not used with standalone builds, and it adds unnecessary
overhead.

Test: without this change, b info no-op takes 24s on my machine. with
this change, it drops to 9s.

Fixes: 251441524
Bug: 243596580
Change-Id: I564629064f51e2b2cad836915aacf6f72e84aaeb
diff --git a/envsetup.sh b/envsetup.sh
index 8b0865d..74d57c2 100644
--- a/envsetup.sh
+++ b/envsetup.sh
@@ -1821,8 +1821,10 @@
             skip_tests=""
         fi
     done
+
     # Generate BUILD, bzl files into the synthetic Bazel workspace (out/soong/workspace).
-    _trigger_build "all-modules" bp2build $skip_tests USE_BAZEL_ANALYSIS= || return 1
+    # RBE is disabled because it's not used with b builds and adds overhead: b/251441524
+    USE_RBE=false _trigger_build "all-modules" bp2build $skip_tests USE_BAZEL_ANALYSIS= || return 1
     # Then, run Bazel using the synthetic workspace as the --package_path.
     if [[ -z "$bazel_args" ]]; then
         # If there are no args, show help and exit.