Restore policy changes in CPMAddPackage (#388)

* Restore policy changes in CPMAddPackage

Fixes #387

* Correct style issues found by CI

cmake/CPM.cmake

@@ -67,6 +67,7 @@ endif()
 
 set_property(GLOBAL PROPERTY CPM_INITIALIZED true)
 
+macro(cpm_set_policies)
   # the policy allows us to change options without caching
   cmake_policy(SET CMP0077 NEW)
   set(CMAKE_POLICY_DEFAULT_CMP0077 NEW)
@@ -83,6 +84,8 @@ if(POLICY CMP0135)
     cmake_policy(SET CMP0135 NEW)
     set(CMAKE_POLICY_DEFAULT_CMP0135 NEW)
   endif()
+endmacro()
+cpm_set_policies()
 
 option(CPM_USE_LOCAL_PACKAGES "Always try to use `find_package` to get dependencies"
        $ENV{CPM_USE_LOCAL_PACKAGES}
@@ -494,6 +497,7 @@ endfunction()
 
 # Download and add a package from source
 function(CPMAddPackage)
+  cpm_set_policies()
 
   list(LENGTH ARGN argnLength)
   if(argnLength EQUAL 1)