When proguard_specs is not None, optimize fails due to divergent logic around R8 and outputs

[pswaminathan]

To reproduce this, add a select or proguard_specs to trigger processing optimizations.

android_binary impl can expect there to be outputs in ctx.outputs:

rules_android/rules/android_binary/impl.bzl

Lines 790 to 792 in 59d7db6

	if ctx.attr._generate_proguard_outputs:
	proguard_output_jar = ctx.outputs.proguard_jar
	proguard_output_config = ctx.outputs.proguard_config

But these outputs are only declared if not using R8 and _generate_proguard_outputs is True:

rules_android/rules/android_binary/rule.bzl

Lines 43 to 53 in 59d7db6

	# proguard_specs is too valuable an attribute to make it nonconfigurable, so if its value is
	# configurable (i.e. of type 'select'), _generate_proguard_outputs will be set to True and the
	# predeclared proguard outputs will be generated. If the proguard_specs attribute resolves to an
	# empty list eventually, we do not use it in the dexing. If user explicitly tries to request it,
	# it will fail.
	if not acls.use_r8(label) and _generate_proguard_outputs:
	outputs["proguard_jar"] = "%{name}_proguard.jar"
	outputs["proguard_config"] = "%{name}_proguard.config"
	if proguard_generate_mapping:
	outputs["proguard_map"] = "%{name}_proguard.map"
	return outputs

Because all ACLs are enabled by default, this means any build with non-None proguard_specs fails with the below:

ERROR: /src/app/main/com/app/BUILD.bazel:230:15: in android_binary rule //src/app/main/com/app:app: 
Traceback (most recent call last):
	File "/private/var/tmp/_bazel_p/38fbac32ce3b415b3947148100343188/external/rules_android~/rules/android_binary/impl.bzl", line 1112, column 35, in impl
		return processing_pipeline.run(ctx, java_package, _PROCESSING_PIPELINE)
	File "/private/var/tmp/_bazel_p/38fbac32ce3b415b3947148100343188/external/rules_android~/rules/processing_pipeline.bzl", line 85, column 23, in _run
		info = execute(ctx, **target_ctx)
	File "/private/var/tmp/_bazel_p/38fbac32ce3b415b3947148100343188/external/rules_android~/rules/android_binary/impl.bzl", line 797, column 42, in _process_optimize
		proguard_output_jar = ctx.outputs.proguard_jar
Error: No attribute 'proguard_jar' in outputs. Make sure you declared a rule output with this name.