cmake: check for python(\d)\.(\d+) when building boost

now that python3.10 has two digits as its minor version, we should be
able to match it.

this change fixes the build with python3.10. without this change, we'd
have

error: wrong library name 'python310' in the --with-<library> option.

when building with python3.10

Signed-off-by: Kefu Chai <tchaikov@gmail.com>

cmake/modules/BuildBoost.cmake

@@ -70,7 +70,7 @@ function(do_build_boost root_dir version)
     if(c MATCHES "^python([0-9])\$")
       set(with_python_version "${CMAKE_MATCH_1}")
       list(APPEND boost_with_libs "python")
-    elseif(c MATCHES "^python([0-9])\\.?([0-9])\$")
+    elseif(c MATCHES "^python([0-9])\\.?([0-9]+)\$")
       set(with_python_version "${CMAKE_MATCH_1}.${CMAKE_MATCH_2}")
       list(APPEND boost_with_libs "python")
     else()