Make running soong_build in alternate modes nicer.

This includes the JSON graph generator and bp2build.

Before:
GENERATE_BAZEL_FILES=1 m nothing
GENERATE_JSON_MODULE_GRAPH=1 m nothing

Now:
m json-module-graph
m bp2build

They can now also be combined with other targets or each other.

The longer-term goal is to run "m queryview" and "m soong_docs" using
the same infrastructure. There are two alternate approaches:

1. Call soong_build from within the main Ninja invocation. This requires
two sequential soong_build invocations and is thus slower.
2. Do everything requested in the same soong_build invocation. This
would be faster, but one AFAIU can't tell Ninja that multiple possible
actions can build the same output so that doesn't work.

(1) is somewhat more desirable because soong_docs seems to be built
from build/make/core/main.mk ; I assume that that can be worked around
although I haven't checked where the output of "m soong_docs" goes.

Test: Presubmits.
Change-Id: If5ba36490d9f3f60733e6d6be9286eb2b67c3ff5
diff --git a/tests/bp2build_bazel_test.sh b/tests/bp2build_bazel_test.sh
index 9bd85a4..379eb65 100755
--- a/tests/bp2build_bazel_test.sh
+++ b/tests/bp2build_bazel_test.sh
@@ -10,10 +10,10 @@
 
 function test_bp2build_null_build() {
   setup
-  run_bp2build
+  run_soong bp2build
   local output_mtime1=$(stat -c "%y" out/soong/.bootstrap/bp2build_workspace_marker)
 
-  run_bp2build
+  run_soong bp2build
   local output_mtime2=$(stat -c "%y" out/soong/.bootstrap/bp2build_workspace_marker)
 
   if [[ "$output_mtime1" != "$output_mtime2" ]]; then
@@ -35,10 +35,10 @@
 EOF
   touch foo/bar/a.txt foo/bar/b.txt
 
-  run_bp2build
+  run_soong bp2build
   local output_mtime1=$(stat -c "%y" out/soong/.bootstrap/bp2build_workspace_marker)
 
-  run_bp2build
+  run_soong bp2build
   local output_mtime2=$(stat -c "%y" out/soong/.bootstrap/bp2build_workspace_marker)
 
   if [[ "$output_mtime1" != "$output_mtime2" ]]; then
@@ -80,7 +80,7 @@
   }
 EOF
 
-  run_bp2build
+  run_soong bp2build
 
   if [[ ! -f "./out/soong/workspace/foo/convertible_soong_module/${GENERATED_BUILD_FILE_NAME}" ]]; then
     fail "./out/soong/workspace/foo/convertible_soong_module/${GENERATED_BUILD_FILE_NAME} was not generated"