Fix iOS cc_library build for protobuf.

The SDK and os versions were hard coded.  Archs were mixed up.
Because of this,  Was getting errors with latest SDK:
clang: warning: no such sysroot directory: '/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS9.2.sdk/' [-Wmissing-sysroot]
clang: warning: no such sysroot directory: '/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS9.2.sdk/' [-Wmissing-sysroot]
clang: warning: no such sysroot directory: '/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS9.2.sdk/' [-Wmissing-sysroot]
In file included from external/com_google_protobuf/src/google/protobuf/io/printer.cc:35:
In file included from external/com_google_protobuf/src/google/protobuf/io/printer.h:40:
In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/string:470:
In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/string_view:171:
In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__string:56:
In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/algorithm:638:
In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/cstring:61:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/string.h:61:15: fatal error: 'string.h' file not found
              ^~~~~~~~~~
              1 error generated.

Currently none of these are needed when using bazel with https://github.com/bazelbuild/rules_apple.
-target arm64-apple-ios is passed properly to clang.  So -arch armv7 etc are not needed.
OS_IOS is not used anywhere.
Sources have:  GOOGLE_PROTOBUF_NO_THREADLOCAL defined in src/google/protobuf/stubs/platform_macros.h for iOS.  So __thread= is not needed.  In fact now that bazel is using C++11 by default,  __thread should ideally be moved to thread_local.
-miphoneos-version-min is passed by rules_apple.

BUILD

@@ -59,37 +59,6 @@ load(
     "internal_protobuf_py_tests",
 )
 
-config_setting(
-    name = "ios_armv7",
-    values = {
-        "ios_cpu": "armv7",
-    },
-)
-
-config_setting(
-    name = "ios_armv7s",
-    values = {
-        "ios_cpu": "armv7s",
-    },
-)
-
-config_setting(
-    name = "ios_arm64",
-    values = {
-        "ios_cpu": "arm64",
-    },
-)
-
-IOS_ARM_COPTS = [
-    "-DOS_IOS",
-    "-miphoneos-version-min=7.0",
-    "-arch armv7",
-    "-arch armv7s",
-    "-arch arm64",
-    "-D__thread=",
-    "-isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS9.2.sdk/",
-]
-
 cc_library(
     name = "protobuf_lite",
     srcs = [
@@ -121,12 +90,7 @@ cc_library(
         "src/google/protobuf/wire_format_lite.cc",
     ],
     hdrs = glob(["src/google/protobuf/**/*.h"]),
-    copts = select({
-        ":ios_armv7": IOS_ARM_COPTS,
-        ":ios_armv7s": IOS_ARM_COPTS,
-        ":ios_arm64": IOS_ARM_COPTS,
-        "//conditions:default": [],
-    }) + COPTS,
+    copts = COPTS,
     includes = ["src/"],
     linkopts = LINK_OPTS,
     visibility = ["//visibility:public"],
@@ -193,12 +157,7 @@ cc_library(
         "src/google/protobuf/wrappers.pb.cc",
     ],
     hdrs = glob(["src/**/*.h"]),
-    copts = select({
-        ":ios_armv7": IOS_ARM_COPTS,
-        ":ios_armv7s": IOS_ARM_COPTS,
-        ":ios_arm64": IOS_ARM_COPTS,
-        "//conditions:default": [],
-    }) + COPTS,
+    copts = COPTS,
     includes = ["src/"],
     linkopts = LINK_OPTS,
     visibility = ["//visibility:public"],