Build BoringSSL without assembly if using MSan.

third_party/boringssl/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Config for us and everybody else depending on BoringSSL.
 config("openssl_config") {
   include_dirs = []
   include_dirs += [ "src/include" ]
   if (is_component_build) {
     defines = [ "BORINGSSL_SHARED_LIBRARY" ]
   }
 }
 
 # Config internal to this build file.
 config("openssl_internal_config") {
   visibility = [ ":*" ]  # Only targets in this file can depend on this.
 }
 
 # The list of BoringSSL files is kept in boringssl.gypi.
 gypi_values =
     exec_script("//build/gypi_to_gn.py",
                 [ rebase_path("//third_party/boringssl/boringssl.gypi") ],
                 "scope",
                 [ "//third_party/boringssl/boringssl.gypi" ])
 
 # Windows' assembly is built with Yasm. The other platforms use the platform
 # assembler.
-if (is_win) {
+if (is_win && !is_msan) {
   import("//third_party/yasm/yasm_assemble.gni")
   yasm_assemble("boringssl_asm") {
     if (current_cpu == "x64") {
       sources = gypi_values.boringssl_win_x86_64_sources
     } else if (current_cpu == "x86") {
       sources = gypi_values.boringssl_win_x86_sources
     }
   }
 }
 
@@ skipping 24 matching lines @@
   # Also gets the include dirs from :openssl_config
   include_dirs = [
     "src/include",
 
     # This is for arm_arch.h, which is needed by some asm files. Since the
     # asm files are generated and kept in a different directory, they
     # cannot use relative paths to find this file.
     "src/crypto",
   ]
 
-  if (current_cpu == "x64") {
+  if (is_msan) {
+    defines += [ "OPENSSL_NO_ASM" ]
+  } else if (current_cpu == "x64") {
     if (is_mac || is_ios) {
       sources += gypi_values.boringssl_mac_x86_64_sources
     } else if (is_linux || is_android) {
       sources += gypi_values.boringssl_linux_x86_64_sources
     } else if (is_win) {
       deps += [ ":boringssl_asm" ]
     } else {
       defines += [ "OPENSSL_NO_ASM" ]
     }
   } else if (current_cpu == "x86") {
     if (is_mac || is_ios) {
       sources += gypi_values.boringssl_mac_x86_sources
     } else if (is_linux || is_android) {
       sources += gypi_values.boringssl_linux_x86_sources
     } else if (is_win) {
       deps += [ ":boringssl_asm" ]
     } else {
       defines += [ "OPENSSL_NO_ASM" ]
     }
   } else if (current_cpu == "arm" && (is_linux || is_android)) {
     sources += gypi_values.boringssl_linux_arm_sources
   } else if (current_cpu == "arm64" && (is_linux || is_android)) {
     sources += gypi_values.boringssl_linux_aarch64_sources
   } else {
     defines += [ "OPENSSL_NO_ASM" ]
   }
 }