build: CMake dependencies handling improved for the freestanding mode

src/CMakeLists.txt

@@ -84,7 +84,8 @@ check_cxx_feature_supported("__cpp_constexpr >= 202211L" ${projectPrefix}STATIC_
 check_cxx_feature_supported(__cpp_explicit_this_parameter ${projectPrefix}EXPLICIT_THIS_PARAMETER_SUPPORTED)
 
 # validate settings
-if(${projectPrefix}API_STD_FORMAT STREQUAL "TRUE"
+if(NOT ${projectPrefix}API_FREESTANDING
+   AND ${projectPrefix}API_STD_FORMAT STREQUAL "TRUE"
    AND NOT
        (${projectPrefix}LIB_FORMAT_SUPPORTED
         # libc++ has a basic supports for std::format but does not set __cpp_lib_format

src/core/CMakeLists.txt

@@ -98,8 +98,9 @@ set_feature_flag(API_STRING_VIEW_RET)
 set_feature_flag(API_NO_CRTP)
 
 # Text formatting
-if(${projectPrefix}API_STD_FORMAT STREQUAL "FALSE" OR (${projectPrefix}API_STD_FORMAT STREQUAL "AUTO"
-                                                       AND NOT ${projectPrefix}LIB_FORMAT_SUPPORTED)
+if(NOT ${projectPrefix}API_FREESTANDING
+   AND (${projectPrefix}API_STD_FORMAT STREQUAL "FALSE" OR (${projectPrefix}API_STD_FORMAT STREQUAL "AUTO"
+                                                            AND NOT ${projectPrefix}LIB_FORMAT_SUPPORTED))
 )
     if(NOT TARGET fmt::fmt)
         find_package(fmt REQUIRED)

src/mp-unitsConfig.cmake

@@ -22,7 +22,7 @@
 
 include(CMakeFindDependencyMacro)
 
-if(NOT MP_UNITS_API_STD_FORMAT)
+if(NOT MP_UNITS_API_FREESTANDING AND NOT MP_UNITS_API_STD_FORMAT)
     find_dependency(fmt)
 endif()