Use target_compile_features() to set C++ standard

This is a better way to enable C++ standard for extensions in this case.
It errors out if C++ compiler doesn't support required standard and it
can be also controlled from the parent project using CMAKE_CXX_STANDARD
variable or through linking. The stricter and newer requirement is
applied in case of different configurations. Using PRIVATE scope to
limit this requirement to extension scope only.

Author: petk

cmake/ext/intl/CMakeLists.txt

@@ -199,19 +199,9 @@ set_package_properties(
 )
 
 if(ICU_VERSION VERSION_GREATER_EQUAL 74)
-  set_target_properties(
-    php_ext_intl
-    PROPERTIES
-      CXX_STANDARD 17
-      CXX_STANDARD_REQUIRED TRUE
-  )
+  target_compile_features(php_ext_intl PRIVATE cxx_std_17)
 else()
-  set_target_properties(
-    php_ext_intl
-    PROPERTIES
-      CXX_STANDARD 11
-      CXX_STANDARD_REQUIRED TRUE
-  )
+  target_compile_features(php_ext_intl PRIVATE cxx_std_11)
 endif()
 
 target_link_libraries(php_ext_intl PRIVATE ICU::io ICU::uc ICU::i18n)