Add support for building NDK modules.

Change-Id: I2c5ede530e40a635e26ae45950580ef450e7dcc6
diff --git a/common/arch.go b/common/arch.go
index a43aa72..02212ad 100644
--- a/common/arch.go
+++ b/common/arch.go
@@ -117,6 +117,7 @@
 	ArchType     ArchType
 	ArchVariant  string
 	CpuVariant   string
+	Abi          string
 }
 
 func (a Arch) String() string {
@@ -234,12 +235,14 @@
 		ArchType:     Arm,
 		ArchVariant:  "armv7-a-neon",
 		CpuVariant:   "cortex-a15",
+		Abi:          "armeabi-v7a",
 	}
 	arm64Arch = Arch{
 		HostOrDevice: Device,
 		ArchType:     Arm64,
 		ArchVariant:  "armv8-a",
 		CpuVariant:   "denver",
+		Abi:          "arm64-v8a",
 	}
 	hostArch = Arch{
 		HostOrDevice: Host,