Fix addrsig warnings

ld -r reorders symbols and invalidates the .llvm_addrsig section, which
then causes warnings if the resulting object is used with ld --icf=safe.
The warning is especially common when building with musl, as the
clang_rt.crt* objects have .llvm_addrsig sections, are linked into
libc_musl_crt* using ld -r, and are then linked into every other binary
and shared library with --icf=safe.

Strip the .llvm_addrsig section after ld -r to prevent the warnings.

Test: m USE_HOST_MUSL=true host-native -k
Change-Id: Ia52a4756b9ebbb62115898d0de9f8641e6fea705

cc/builder.go

@@ -125,6 +125,14 @@ var (
 		},
 		"objcopyCmd", "prefix")
 
+	// Rule to run objcopy --remove-section=.llvm_addrsig on a partially linked object
+	noAddrSig = pctx.AndroidStaticRule("noAddrSig",
+		blueprint.RuleParams{
+			Command:     "rm -f ${out} && $objcopyCmd --remove-section=.llvm_addrsig ${in} ${out}",
+			CommandDeps: []string{"$objcopyCmd"},
+		},
+		"objcopyCmd")
+
 	_ = pctx.SourcePathVariable("stripPath", "build/soong/scripts/strip.sh")
 	_ = pctx.SourcePathVariable("xzCmd", "prebuilts/build-tools/${config.HostPrebuiltTag}/bin/xz")
 	_ = pctx.SourcePathVariable("createMiniDebugInfo", "prebuilts/build-tools/${config.HostPrebuiltTag}/bin/create_minidebuginfo")
@@ -1008,6 +1016,21 @@ func transformBinaryPrefixSymbols(ctx android.ModuleContext, prefix string, inpu
 	})
 }
 
+// Generate a rule for running objcopy --remove-section=.llvm_addrsig on a partially linked object
+func transformObjectNoAddrSig(ctx android.ModuleContext, inputFile android.Path, outputFile android.WritablePath) {
+	objcopyCmd := "${config.ClangBin}/llvm-objcopy"
+
+	ctx.Build(pctx, android.BuildParams{
+		Rule:        noAddrSig,
+		Description: "remove addrsig " + outputFile.Base(),
+		Output:      outputFile,
+		Input:       inputFile,
+		Args: map[string]string{
+			"objcopyCmd": objcopyCmd,
+		},
+	})
+}
+
 // Registers a build statement to invoke `strip` (to discard symbols and data from object files).
 func transformStrip(ctx android.ModuleContext, inputFile android.Path,
 	outputFile android.WritablePath, flags StripFlags) {