bp2build support for host_ldlibs

host_ldlibs are used during linking. Set these in `linkopts` for now.

Note that this CL does not do the `CheckBadHostLdLibs` validation of
Soong. There are some different ways to do this, and these are being
discussed in b/216626461. It is likely that we will need to create a new
property `host_ldlibs` to do the validation. But for now, re-use
`linkopts`.

Bug: 216626461
Test: bp2build unit tests
Change-Id: Id4c77e4460fb1fb003fa58ea27bab5b50ea8cefe

bazel/configurability.go

@@ -31,11 +31,11 @@ const (
 
 	// OsType names in arch.go
 	OsAndroid     = "android"
-	osDarwin      = "darwin"
-	osLinux       = "linux_glibc"
+	OsDarwin      = "darwin"
+	OsLinux       = "linux_glibc"
 	osLinuxMusl   = "linux_musl"
 	osLinuxBionic = "linux_bionic"
-	osWindows     = "windows"
+	OsWindows     = "windows"
 
 	// Targets in arch.go
 	osArchAndroidArm        = "android_arm"
@@ -156,11 +156,11 @@ var (
 	// constraint_value for the @platforms//os:os constraint_setting
 	platformOsMap = map[string]string{
 		OsAndroid:                  "//build/bazel/platforms/os:android",
-		osDarwin:                   "//build/bazel/platforms/os:darwin",
-		osLinux:                    "//build/bazel/platforms/os:linux_glibc",
+		OsDarwin:                   "//build/bazel/platforms/os:darwin",
+		OsLinux:                    "//build/bazel/platforms/os:linux_glibc",
 		osLinuxMusl:                "//build/bazel/platforms/os:linux_musl",
 		osLinuxBionic:              "//build/bazel/platforms/os:linux_bionic",
-		osWindows:                  "//build/bazel/platforms/os:windows",
+		OsWindows:                  "//build/bazel/platforms/os:windows",
 		ConditionsDefaultConfigKey: ConditionsDefaultSelectKey, // The default condition of an os select map.
 	}
 
@@ -192,22 +192,22 @@ var (
 	// in a cyclic dependency.
 	osToArchMap = map[string][]string{
 		OsAndroid:     {archArm, archArm64, archRiscv64, archX86, archX86_64},
-		osLinux:       {archX86, archX86_64},
+		OsLinux:       {archX86, archX86_64},
 		osLinuxMusl:   {archX86, archX86_64},
-		osDarwin:      {archArm64, archX86_64},
+		OsDarwin:      {archArm64, archX86_64},
 		osLinuxBionic: {archArm64, archX86_64},
 		// TODO(cparsons): According to arch.go, this should contain archArm, archArm64, as well.
-		osWindows: {archX86, archX86_64},
+		OsWindows: {archX86, archX86_64},
 	}
 
 	osAndInApexMap = map[string]string{
 		AndroidAndInApex:           "//build/bazel/rules/apex:android-in_apex",
 		AndroidPlatform:            "//build/bazel/rules/apex:system",
-		osDarwin:                   "//build/bazel/platforms/os:darwin",
-		osLinux:                    "//build/bazel/platforms/os:linux_glibc",
+		OsDarwin:                   "//build/bazel/platforms/os:darwin",
+		OsLinux:                    "//build/bazel/platforms/os:linux_glibc",
 		osLinuxMusl:                "//build/bazel/platforms/os:linux_musl",
 		osLinuxBionic:              "//build/bazel/platforms/os:linux_bionic",
-		osWindows:                  "//build/bazel/platforms/os:windows",
+		OsWindows:                  "//build/bazel/platforms/os:windows",
 		ConditionsDefaultConfigKey: ConditionsDefaultSelectKey,
 	}
 

bp2build/cc_library_conversion_test.go

@@ -4657,3 +4657,49 @@ cc_library {
 		},
 	})
 }
+
+func TestCcLibraryHostLdLibs(t *testing.T) {
+	runCcLibraryTestCase(t, Bp2buildTestCase{
+		Description:                "cc_binary linker flags for host_ldlibs",
+		ModuleTypeUnderTest:        "cc_binary",
+		ModuleTypeUnderTestFactory: cc.BinaryFactory,
+		Blueprint: soongCcLibraryPreamble + `cc_binary {
+    name: "a",
+    host_supported: true,
+    ldflags: ["-lcommon"],
+    target: {
+	linux: {
+		host_ldlibs: [
+			"-llinux",
+		],
+	},
+	darwin: {
+		ldflags: ["-ldarwinadditional"],
+		host_ldlibs: [
+			"-ldarwin",
+		],
+	},
+	windows: {
+		host_ldlibs: [
+			"-lwindows",
+		],
+	},
+    },
+}
+`,
+		ExpectedBazelTargets: []string{
+			MakeBazelTargetNoRestrictions("cc_binary", "a", AttrNameToString{
+				"linkopts": `["-lcommon"] + select({
+        "//build/bazel/platforms/os:darwin": [
+            "-ldarwinadditional",
+            "-ldarwin",
+        ],
+        "//build/bazel/platforms/os:linux_glibc": ["-llinux"],
+        "//build/bazel/platforms/os:windows": ["-lwindows"],
+        "//conditions:default": [],
+    })`,
+				"local_includes": `["."]`,
+			}),
+		},
+	})
+}

cc/bp2build.go

@@ -1254,6 +1254,9 @@ func (la *linkerAttributes) bp2buildForAxisAndConfig(ctx android.BazelConversion
 	}
 
 	la.additionalLinkerInputs.SetSelectValue(axis, config, additionalLinkerInputs)
+	if axis == bazel.OsConfigurationAxis && (config == bazel.OsDarwin || config == bazel.OsLinux || config == bazel.OsWindows) {
+		linkerFlags = append(linkerFlags, props.Host_ldlibs...)
+	}
 	la.linkopts.SetSelectValue(axis, config, linkerFlags)
 
 	if axisFeatures != nil {