Python3的CMake find_包在查找Python2时失败

Question

在迁移到CMake 3.17.3（从3.13.3）时，我们偶然发现了Python的一个问题。在根目录CMakeLists.txt中，我们现在有：

find_package(Python3 REQUIRED COMPONENTS Interpreter)

但是，这在以下情况下失败：

CMake Error at /home/abadura/cmake/cmake-3.17.3-Linux-x86_64/share/cmake-3.17/Modules/FindPackageHandleStandardArgs.cmake:164 (message):
  Could NOT find Python3 (missing: Python3_EXECUTABLE Interpreter)

      Reason given by package: 
          Interpreter: Wrong major version for the interpreter "/build/ltesdkroot/Platforms/LINUX/MB_PS_LFS_REL_2020_07_0068/sdk/bld-tools/x86_64-pc-linux-gnu/bin/python"

Call Stack (most recent call first):
  /home/abadura/cmake/cmake-3.17.3-Linux-x86_64/share/cmake-3.17/Modules/FindPackageHandleStandardArgs.cmake:445 (_FPHSA_FAILURE_MESSAGE)
  /home/abadura/cmake/cmake-3.17.3-Linux-x86_64/share/cmake-3.17/Modules/FindPython/Support.cmake:2437 (find_package_handle_standard_args)
  /home/abadura/cmake/cmake-3.17.3-Linux-x86_64/share/cmake-3.17/Modules/FindPython3.cmake:309 (include)
  CMakeLists.txt:20 (find_package)

而Python发现（/build/ltesdkroot/Platforms/LINUX/MB_PS_LFS_REL_2020_07_0068/sdk/bld-tools/x86_64-pc-linux-gnu/bin/python）报告版本Python 2.7.15+

通过搜索和实验，我发现添加：

set(Python3_FIND_STRATEGY VERSION)

在find_package帮助之前。通过此添加的Python，可以找到：

-- Found Python3: /opt/python/x86_64/3.6.0/bin-wrapped/python3.6 (found version "3.6.0") found components: Interpreter 

现在，问题是FindPython3 documentation陈述了以下内容：

Python3_FIND_STRATEGY

This variable defines how lookup will be done. The Python3_FIND_STRATEGY variable can be set to one of the following:

• VERSION: Try to find the most recent version in all specified locations. This is the default if policy CMP0094 is undefined or set to OLD.
• LOCATION: Stops lookup as soon as a version satisfying version constraints is founded. This is the default if policy CMP0094 is set to NEW.

因此，基于我对描述的理解，LOCATION应该可以正常工作。它应该忽略/build/ltesdkroot/Platforms/LINUX/MB_PS_LFS_REL_2020_07_0068/sdk/bld-tools/x86_64-pc-linux-gnu/bin/python，因为它不满足版本约束（它是python2而不是pytho3），并且应该继续查找满足约束的/opt/python/x86_64/3.6.0/bin-wrapped/python3.6。（为了完整性，我尝试在find_package中添加显式的3.6版本，但它没有改变任何东西。）

另一个问题是我应该设置Python3_FIND_STRATEGY还是直接使用CMP0094。{a2}文档有一个有点可怕的警告：

Note The OLD behavior of a policy is deprecated by definition and may be removed in a future version of CMake.

因此，我不确定哪种方法（为CMP0094设置Python3_FIND_STRATEGY或激活OLD）是理想的（稳定的）方法