Rules for s390x

[gongsu832]

Hi, boost runs on s390x Linux. Can we add rules for BOOST_CTX_ASM_SOURCES in BUILD.boost for s390x? Thanks.

*** BUILD.boost.orig	2022-03-07 09:58:21.384488616 -0500
--- BUILD.boost	2022-03-07 11:36:52.711836065 -0500
***************
*** 130,135 ****
--- 130,144 ----
      visibility = ["//visibility:public"],
  )

+ config_setting(
+     name = "linux_s390x",
+     constraint_values = [
+         "@bazel_tools//platforms:linux",
+         "@bazel_tools//platforms:s390x",
+     ],
+     visibility = ["//visibility:public"],
+ )
+
  # Rename .asm to .S so that it will be handled with the C preprocessor.
  [copy_file(
      name = "rename_%s" % name,
***************
*** 177,182 ****
--- 186,196 ----
          "libs/context/src/asm/jump_x86_64_ms_pe_masm.S",
          "libs/context/src/asm/ontop_x86_64_ms_pe_masm.S",
      ],
+     ":linux_s390x": [
+         "libs/context/src/asm/make_s390x_sysv_elf_gas.S",
+         "libs/context/src/asm/jump_s390x_sysv_elf_gas.S",
+         "libs/context/src/asm/ontop_s390x_sysv_elf_gas.S",
+     ],
      "//conditions:default": [],
  })