bp2build: Handle export_generated_header property

The generated_header property resides in BaseCompilerProperties, while
export_generated_header resides in BaseLinkerProperties. Previously
bp2build handled these property structs separately; however, these two
related properties residing in separate structs requires restructuring
the code to allow access to both BaseCompilerProperties and
BaseLinkerProperties for a single axis/configuration combination to
resolve which generated headers are exported/not for the
axis/configuration..

Test: go test soong tests
Test: build/bazel/ci/bp2build.sh
Change-Id: Id150003637fd19d87e8dc5d6941e9f36dc4031dd
diff --git a/cc/library_headers.go b/cc/library_headers.go
index b2b3dbc..ede6ab3 100644
--- a/cc/library_headers.go
+++ b/cc/library_headers.go
@@ -132,7 +132,8 @@
 	}
 
 	exportedIncludes := bp2BuildParseExportedIncludes(ctx, module)
-	linkerAttrs := bp2BuildParseLinkerProps(ctx, module)
+	baseAttributes := bp2BuildParseBaseProps(ctx, module)
+	linkerAttrs := baseAttributes.linkerAttributes
 
 	attrs := &bazelCcLibraryHeadersAttributes{
 		Export_includes:        exportedIncludes.Includes,
@@ -140,6 +141,7 @@
 		Implementation_deps:    linkerAttrs.implementationDeps,
 		Deps:                   linkerAttrs.deps,
 		System_dynamic_deps:    linkerAttrs.systemDynamicDeps,
+		Hdrs:                   baseAttributes.hdrs,
 	}
 
 	props := bazel.BazelTargetModuleProperties{