Added module for abi constraint values

BUILD

@@ -9,6 +9,7 @@ filegroup(
     srcs = [
         "BUILD",
         "WORKSPACE",
+        "//abi:srcs",
         "//cpu:srcs",
         "//os:srcs",
     ],

abi/BUILD

@@ -0,0 +1,114 @@
+# Standard constraint_setting and constraint_values to be used in platforms.
+licenses(["notice"])
+
+package(
+    default_visibility = ["//visibility:public"],
+)
+
+filegroup(
+    name = "srcs",
+    srcs = glob(["**"]),
+)
+
+# To add a new constraint_value see https://github.com/bazelbuild/platforms.
+constraint_setting(name = "abi")
+
+constraint_value(
+    name = "atmega328",
+    constraint_setting = ":abi",
+)
+
+constraint_value(
+    name = "eabi",
+    constraint_setting = ":abi",
+)
+
+constraint_value(
+    name = "eabihf",
+    constraint_setting = ":abi",
+)
+
+constraint_value(
+    name = "elf",
+    constraint_setting = ":abi",
+)
+
+constraint_value(
+    name = "gnu",
+    constraint_setting = ":abi",
+)
+
+constraint_value(
+    name = "gnu_ilp32",
+    constraint_setting = ":abi",
+)
+
+constraint_value(
+    name = "gnueabi",
+    constraint_setting = ":abi",
+)
+
+constraint_value(
+    name = "gnuabi64",
+    constraint_setting = ":abi",
+)
+
+constraint_value(
+    name = "gnueabihf",
+    constraint_setting = ":abi",
+)
+
+constraint_value(
+    name = "gnux32",
+    constraint_setting = ":abi",
+)
+
+constraint_value(
+    name = "linuxkernel",
+    constraint_setting = ":abi",
+)
+
+constraint_value(
+    name = "musl",
+    constraint_setting = ":abi",
+)
+
+constraint_value(
+    name = "muslabi64",
+    constraint_setting = ":abi",
+)
+
+constraint_value(
+    name = "musleabi",
+    constraint_setting = ":abi",
+)
+
+constraint_value(
+    name = "musleabihf",
+    constraint_setting = ":abi",
+)
+
+constraint_value(
+    name = "sgx",
+    constraint_setting = ":abi",
+)
+
+constraint_value(
+    name = "softfloat",
+    constraint_setting = ":abi",
+)
+
+constraint_value(
+    name = "uclibc",
+    constraint_setting = ":abi",
+)
+
+constraint_value(
+    name = "uclibceabi",
+    constraint_setting = ":abi",
+)
+
+constraint_value(
+    name = "uclibceabihf",
+    constraint_setting = ":abi",
+)