Merge "Allow profiling Soong from the full build"

### Soong

Soong can be traced and profiled using the standard Go tools. It understands

the `-cpuprofile`, `-trace`, and `-memprofile` command line arguments, but we

don't currently have an easy way to enable them in the context of a full build.

Soong proper (i.e., `soong_build` executable that processes the blueprint

files) can be traced and profiled using the standard Go tools. It understands

the `-trace`, `-cpuprofile`, and `-memprofile` command line arguments.

Setting `SOONG_PROFILE_CPU` and/or `SOONG_PROFILE_MEM` environment variables

for the build enables respective profiling, e.g., running

```shell

SOONG_PROFILE_CPU=/tmp/foo m ..._

```

saves CPU profile for each Soong invocation in /tmp/foo._step_ file, where

_step_ is Soong execution step. The main step is `build`. The others as

`bp2build_files`, `bp2build_workspace`, `modulegraph`, `queryview`,

`api_bp2build`, `soong_docs` (not all of them necessarily run during the build).

The profiles can be inspected with `go tool pprof` from the command line or

with _Run>Open Profiler Snapshot_ in IntelliJ IDEA.

### Kati

	allArgs = append(allArgs, commonArgs...)

	allArgs = append(allArgs, environmentArgs(config, name)...)

	if profileCpu := os.Getenv("SOONG_PROFILE_CPU"); profileCpu != "" {

		allArgs = append(allArgs, "--cpuprofile", profileCpu+"."+name)

	}

	if profileMem := os.Getenv("SOONG_PROFILE_MEM"); profileMem != "" {

		allArgs = append(allArgs, "--memprofile", profileMem+"."+name)

	}

	allArgs = append(allArgs, "Android.bp")

	return bootstrap.PrimaryBuilderInvocation{