[python] Bump Python minimum version to 3.8

As per the RFC
https://discourse.llvm.org/t/rfc-upgrading-llvms-minimum-required-python-version/67571,
raise the minimum Python version to ensure that the Python syntax doesn't
become overly obsolete, to enable new Python feature usage, and ensure the
maintainability of CI.

Author: linux4life798

llvm/CMakeLists.txt

@@ -881,7 +881,7 @@ set(LLVM_PROFDATA_FILE "" CACHE FILEPATH
 
 if(LLVM_INCLUDE_TESTS)
   # All LLVM Python files should be compatible down to this minimum version.
-  set(LLVM_MINIMUM_PYTHON_VERSION 3.7)
+  set(LLVM_MINIMUM_PYTHON_VERSION 3.8)
 else()
   # FIXME: it is unknown if this is the actual minimum bound
   set(LLVM_MINIMUM_PYTHON_VERSION 3.0)

llvm/docs/GettingStarted.rst

@@ -286,7 +286,7 @@ uses the package and provides other details.
 Package                                                     Version      Notes
 =========================================================== ============ ==========================================
 `CMake <http://cmake.org/>`__                               >=3.20.0     Makefile/workspace generator
-`python <http://www.python.org/>`_                          >=3.7        Automated test suite\ :sup:`1`
+`python <http://www.python.org/>`_                          >=3.8        Automated test suite\ :sup:`1`
 `zlib <http://zlib.net>`_                                   >=1.2.3.4    Compression library\ :sup:`2`
 `GNU Make <http://savannah.gnu.org/projects/make>`_         3.79, 3.79.1 Makefile/build processor\ :sup:`3`
 =========================================================== ============ ==========================================