Disable relocation_packer and migrate to SHT_RELR sections.

Proposal for adding SHT_RELR sections in the generic-abi is at
https://groups.google.com/forum/#!topic/generic-abi/bX460iggiKg

Comparison with relocation_packer for aosp_marlin-userdebug:
$ du -B1 -s */out/target/product/marlin/system
 996958208      base/out/target/product/marlin/system
1008340992      no_pack/out/target/product/marlin/system
 997801984      sht_relr/out/target/product/marlin/system

base contains a build with current settings.
no_pack contains a build with relocation_packer disabled.
sht_relr contains a build with SHT_RELR sections enabled.

relocation_packer was saving 11,382,784 bytes (no_pack - base).
SHT_RELR sections are saving 10,539,008 bytes (no_pack - sht_relr).

Bug: None
Test: Built aosp_marlin-userdebug image, boots on device.
Test: Built aosp_x86_64-userdebug image, boots in emulator.
Change-Id: I448dc95baa4976b68ce2659b80498539426775f9

cc/config/arm64_device.go

@@ -33,6 +33,7 @@ var (
 		"-Wl,--fix-cortex-a53-843419",
 		"-fuse-ld=gold",
 		"-Wl,--icf=safe",
+		"-Wl,--experimental-use-relr",
 	}
 
 	arm64Cppflags = []string{}

cc/config/arm_device.go

@@ -37,6 +37,7 @@ var (
 		"-Wl,--icf=safe",
 		"-Wl,--hash-style=gnu",
 		"-Wl,-m,armelf",
+		"-Wl,--experimental-use-relr",
 	}
 
 	armArmCflags = []string{

cc/config/x86_64_device.go

@@ -30,6 +30,7 @@ var (
 
 	x86_64Ldflags = []string{
 		"-Wl,--hash-style=gnu",
+		"-Wl,--experimental-use-relr",
 	}
 
 	x86_64ArchVariantCflags = map[string][]string{

cc/relocation_packer.go

@@ -45,7 +45,14 @@ type relocationPacker struct {
 }
 
 func (p *relocationPacker) packingInit(ctx BaseModuleContext) {
-	enabled := true
+	// Disable relocation_packer and migrate to SHT_RELR sections.
+	//
+	// Proposal for adding SHT_RELR sections in generic-abi is at
+	// https://groups.google.com/forum/#!topic/generic-abi/bX460iggiKg
+	//
+	// TODO: Remove relocation_packer and associated build logic.
+	enabled := false
+
 	// Relocation packer isn't available on Darwin yet
 	if runtime.GOOS == "darwin" {
 		enabled = false