Replace GENERATE_BAZEL_FILES=1 with "m bp2build".

This should have been submitted in the pertinent topic, but I messed by
git repositories up.

Test: Presubmits.
Change-Id: I7f3e9648c1961169ff40c8e2ddaf3d893498f625
diff --git a/envsetup.sh b/envsetup.sh
index 6085f7a..d70e815 100644
--- a/envsetup.sh
+++ b/envsetup.sh
@@ -1707,7 +1707,7 @@
 function b()
 (
     # Generate BUILD, bzl files into the synthetic Bazel workspace (out/soong/workspace).
-    _trigger_build "all-modules" nothing GENERATE_BAZEL_FILES=true USE_BAZEL_ANALYSIS= || return 1
+    _trigger_build "all-modules" bp2build USE_BAZEL_ANALYSIS= || return 1
     # Then, run Bazel using the synthetic workspace as the --package_path.
     if [[ -z "$@" ]]; then
         # If there are no args, show help.