cmake: add module that detects hardware arch

Required by the following commit.

cmake/SetHardwareArch.cmake

@@ -0,0 +1,59 @@
+# Copyright 2020 The SwiftShader Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+#            x32       x86_64
+# ----------------------------
+# ARM        arm       aarch64
+# MIPS       mipsel    mips64el
+# PPC        ppcle     ppc64le
+# Intel-x86  x86       x86_64
+
+if(CMAKE_SYSTEM_PROCESSOR MATCHES "arm" OR
+   CMAKE_SYSTEM_PROCESSOR MATCHES "aarch")
+  if(CMAKE_SIZEOF_VOID_P EQUAL 8)
+    set(HW_ARCH "aarch64")
+  else()
+    set(HW_ARCH "arm")
+  endif()
+elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "^mips.*")
+  if(CMAKE_SIZEOF_VOID_P EQUAL 8)
+    set(HW_ARCH "mips64el")
+  else()
+    set(HW_ARCH "mipsel")
+  endif()
+elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "^ppc.*")
+  if(CMAKE_SIZEOF_VOID_P EQUAL 8)
+    set(HW_ARCH "ppc64le")
+  else()
+    set(HW_ARCH "ppcle")
+  endif()
+else()
+  if(CMAKE_SIZEOF_VOID_P EQUAL 8)
+    set(HW_ARCH "x86_64")
+  else()
+    set(HW_ARCH "x86")
+  endif()
+endif()
+
+if(CMAKE_OSX_ARCHITECTURES)
+  if(CMAKE_OSX_ARCHITECTURES MATCHES "arm64")
+    set(HW_ARCH "aarch64")
+  elseif(CMAKE_OSX_ARCHITECTURES MATCHES "x86_64")
+    set(HW_ARCH "x86_64")
+  elseif(CMAKE_OSX_ARCHITECTURES MATCHES "i386")
+    set(HW_ARCH "x86")
+  else()
+    message(FATAL_ERROR "Unsupported hardware architecture")
+  endif()
+endif()