bp2build support for stem

By default, the artifacts generated by cc_binary and cc_library in Soong
track the module name. But Soong supports overidding this using the stem
property. e.g.
```
cc_library {
  name: "foo.1.2",
  stem: "foo",
}
```
will generate foo.so

This CL adds this property to bp2build

Test: bp2build unit tests
Bug: 240563612
Change-Id: I1dfed870d5bad450511b72c397d2355c01fa3b60

bp2build/cc_binary_conversion_test.go

@@ -1106,3 +1106,40 @@ func TestCcBinaryWithCfiAndCfiAssemblySupport(t *testing.T) {
 		},
 	})
 }
+
+func TestCcBinaryStem(t *testing.T) {
+	runCcBinaryTestCase(t, ccBinaryBp2buildTestCase{
+		description: "cc_binary with stem property",
+		blueprint: `
+cc_binary {
+	name: "foo_with_stem_simple",
+	stem: "foo",
+}
+cc_binary {
+	name: "foo_with_arch_variant_stem",
+	arch: {
+		arm: {
+			stem: "foo-arm",
+		},
+		arm64: {
+			stem: "foo-arm64",
+		},
+	},
+}
+`,
+		targets: []testBazelTarget{
+			{"cc_binary", "foo_with_stem_simple", AttrNameToString{
+				"stem":           `"foo"`,
+				"local_includes": `["."]`,
+			}},
+			{"cc_binary", "foo_with_arch_variant_stem", AttrNameToString{
+				"stem": `select({
+        "//build/bazel/platforms/arch:arm": "foo-arm",
+        "//build/bazel/platforms/arch:arm64": "foo-arm64",
+        "//conditions:default": None,
+    })`,
+				"local_includes": `["."]`,
+			}},
+		},
+	})
+}

bp2build/cc_library_conversion_test.go

@@ -4812,3 +4812,42 @@ cc_library {
 		},
 	})
 }
+
+func TestCcLibraryWithStem(t *testing.T) {
+	runCcLibraryTestCase(t, Bp2buildTestCase{
+		Description:                "cc_library with stem property",
+		ModuleTypeUnderTest:        "cc_library_shared",
+		ModuleTypeUnderTestFactory: cc.LibrarySharedFactory,
+		Blueprint: soongCcLibraryPreamble + `
+cc_library_shared {
+	name: "foo_with_stem_simple",
+	stem: "foo",
+}
+cc_library_shared {
+	name: "foo_with_arch_variant_stem",
+	arch: {
+		arm: {
+			stem: "foo-arm",
+		},
+		arm64: {
+			stem: "foo-arm64",
+		},
+	},
+}
+`,
+		ExpectedBazelTargets: []string{
+			MakeBazelTarget("cc_library_shared", "foo_with_stem_simple", AttrNameToString{
+				"stem":           `"foo"`,
+				"local_includes": `["."]`,
+			}),
+			MakeBazelTarget("cc_library_shared", "foo_with_arch_variant_stem", AttrNameToString{
+				"stem": `select({
+        "//build/bazel/platforms/arch:arm": "foo-arm",
+        "//build/bazel/platforms/arch:arm64": "foo-arm64",
+        "//conditions:default": None,
+    })`,
+				"local_includes": `["."]`,
+			}),
+		},
+	})
+}

cc/bp2build.go

@@ -434,6 +434,7 @@ type compilerAttributes struct {
 
 	features bazel.StringListAttribute
 
+	stem   bazel.StringAttribute
 	suffix bazel.StringAttribute
 
 	fdoProfile bazel.LabelAttribute
@@ -819,6 +820,9 @@ func bp2BuildParseBaseProps(ctx android.Bp2buildMutatorContext, module *Module)
 						compilerAttrs.stubsVersions.SetSelectValue(axis, cfg, versions)
 					}
 				}
+				if stem := libraryProps.Stem; stem != nil {
+					compilerAttrs.stem.SetSelectValue(axis, cfg, stem)
+				}
 				if suffix := libraryProps.Suffix; suffix != nil {
 					compilerAttrs.suffix.SetSelectValue(axis, cfg, suffix)
 				}
@@ -1737,6 +1741,7 @@ func bazelLabelForSharedDepsExcludes(ctx android.BazelConversionPathContext, mod
 
 type binaryLinkerAttrs struct {
 	Linkshared *bool
+	Stem       bazel.StringAttribute
 	Suffix     bazel.StringAttribute
 }
 
@@ -1754,6 +1759,9 @@ func bp2buildBinaryLinkerProps(ctx android.BazelConversionPathContext, m *Module
 			// nonconfigurable attribute. Only 4 AOSP modules use this feature, defer handling
 			ctx.ModuleErrorf("bp2build cannot migrate a module with arch/target-specific static_executable values")
 		}
+		if stem := linkerProps.Stem; stem != nil {
+			attrs.Stem.SetSelectValue(axis, config, stem)
+		}
 		if suffix := linkerProps.Suffix; suffix != nil {
 			attrs.Suffix.SetSelectValue(axis, config, suffix)
 		}

cc/library.go

@@ -408,6 +408,7 @@ func libraryBp2Build(ctx android.TopDownMutatorContext, m *Module) {
 		sharedTargetAttrs.Stubs_symbol_file = compilerAttrs.stubsSymbolFile
 	}
 
+	sharedTargetAttrs.Stem = compilerAttrs.stem
 	sharedTargetAttrs.Suffix = compilerAttrs.suffix
 
 	for axis, configToProps := range m.GetArchVariantProperties(ctx, &LibraryProperties{}) {
@@ -2987,6 +2988,7 @@ func sharedOrStaticLibraryBp2Build(ctx android.TopDownMutatorContext, module *Mo
 
 			Features: *features,
 
+			Stem:   compilerAttrs.stem,
 			Suffix: compilerAttrs.suffix,
 
 			bazelCcHeaderAbiCheckerAttributes: bp2buildParseAbiCheckerProps(ctx, module),
@@ -3072,6 +3074,7 @@ type bazelCcLibrarySharedAttributes struct {
 
 	Inject_bssl_hash bazel.BoolAttribute
 
+	Stem   bazel.StringAttribute
 	Suffix bazel.StringAttribute
 
 	bazelCcHeaderAbiCheckerAttributes