Be compatible with CMake 3.10 again (#2296)

* Be compatible with CMake 3.10 again

* Windows fix

* Add CMake changes to patch file

BUILDING.md

@@ -4,7 +4,7 @@
 
 To build Filament, you must first install the following tools:
 
-- CMake 3.12 (or more recent)
+- CMake 3.10 (or more recent)
 - clang 7.0 (or more recent)
 - [ninja 1.8](https://github.com/ninja-build/ninja/wiki/Pre-built-Ninja-packages) (or more recent)
 

build.sh

@@ -75,7 +75,7 @@ function print_help {
 
 # Requirements
 CMAKE_MAJOR=3
-CMAKE_MINOR=12
+CMAKE_MINOR=10
 ANDROID_NDK_VERSION=21
 
 # Internal variables

third_party/spirv-tools/CMakeLists.txt

@@ -201,10 +201,10 @@ if(NOT COMMAND find_host_program)
 endif()
 
 # Tests require Python3
-if (${CMAKE_SYSTEM_NAME} MATCHES "Windows")
+if(CMAKE_VERSION VERSION_LESS "3.12" OR ${CMAKE_SYSTEM_NAME} MATCHES "Windows")
   find_host_package(PythonInterp 3 REQUIRED)
 else()
-  find_package (Python3 COMPONENTS Interpreter)
+  find_package(Python3 COMPONENTS Interpreter)
 endif()
 
 # Check for symbol exports on Linux.

third_party/spirv-tools/filament-specific-changes.patch

@@ -116,3 +116,16 @@ index 6ed56a81..2392dfd8 100755
 
  # Install pkg-config file
  if (ENABLE_SPIRV_TOOLS_INSTALL)
+@@ -201,7 +201,11 @@ if(NOT COMMAND find_host_program)
+ endif()
+
+ # Tests require Python3
+-find_host_package(PythonInterp 3 REQUIRED)
++if(CMAKE_VERSION VERSION_LESS "3.12" OR ${CMAKE_SYSTEM_NAME} MATCHES "Windows")
++  find_host_package(PythonInterp 3 REQUIRED)
++else()
++  find_package(Python3 COMPONENTS Interpreter)
++endif()
+
+ # Check for symbol exports on Linux.
+ # At the moment, this check will fail on the OSX build machines for the Android NDK.