Remove the out/soong/.bootstrap directory.

It's better not to have state hidden in dotfiles (or rather,
dotdirectories) if we can help.

It's questionable whether the "linux-x86" path segment makes sense since
soong_build only ever runs on one operating system, but I didn't want to
rock the boat now.

Drive-by fixed some quoting fixes in rbc-run. Notably, I didn't wrap
`$@` into double quotes because I don't know whether the lack of double
quotes was intended or not.

Also drive-by fixed the fact that "out/soong" was added twice to the
directory name of bpglob. This turned out not to be a problem because
bpglob doesn't need to be explicitly built: if it's needed, it's
declared as an input of the glob files so it'll be built automatically
(at the cost of the first "null build" not actually being a null build)

Test: Presubmits.
Change-Id: I710d8d16cd8212059a0ca1ee95378505303eed83
diff --git a/ui/build/test_build.go b/ui/build/test_build.go
index f9a60b6..83007be 100644
--- a/ui/build/test_build.go
+++ b/ui/build/test_build.go
@@ -63,7 +63,6 @@
 	cmd.StartOrFatal()
 
 	outDir := config.OutDir()
-	bootstrapDir := filepath.Join(outDir, "soong", ".bootstrap")
 	modulePathsDir := filepath.Join(outDir, ".module_paths")
 	variablesFilePath := filepath.Join(outDir, "soong", "soong.variables")
 
@@ -86,8 +85,7 @@
 			// Leaf node is not in the out directory.
 			continue
 		}
-		if strings.HasPrefix(line, bootstrapDir) ||
-			strings.HasPrefix(line, modulePathsDir) ||
+		if strings.HasPrefix(line, modulePathsDir) ||
 			line == variablesFilePath ||
 			line == dexpreoptConfigFilePath ||
 			line == buildDatetimeFilePath {