try_compile: Do not use CMAKE_BUILD_TYPE or CMAKE_CONFIGURATION_TYPES env vars

Since:

* commit e216b9bbd3 (cmake: Allow CMAKE_BUILD_TYPE to be set by
                     environment variable, 2021-06-29, v3.22.0-rc1~503^2~1)
* commit ef56eefc9b (cmake: Allow CMAKE_CONFIGURATION_TYPES to be set by
                     environment variable, 2021-06-29, v3.22.0-rc1~503^2)

the environment variables are supposed to provide defaults for settings
the user otherwise can control via cache entries.  However, they
accidentally affect `try_compile` projects too, which are supposed to be
programmatically controlled.

Fixes: #22935

Source/cmGlobalGenerator.cxx

@@ -498,7 +498,8 @@ bool cmGlobalGenerator::CheckLanguages(
 void cmGlobalGenerator::EnableLanguage(
   std::vector<std::string> const& languages, cmMakefile* mf, bool optional)
 {
-  if (!this->IsMultiConfig()) {
+  if (!this->IsMultiConfig() &&
+      !this->GetCMakeInstance()->GetIsInTryCompile()) {
     std::string envBuildType;
     if (!mf->GetDefinition("CMAKE_BUILD_TYPE") &&
         cmSystemTools::GetEnv("CMAKE_BUILD_TYPE", envBuildType)) {

Source/cmMakefile.cxx

@@ -3167,7 +3167,8 @@ void cmMakefile::InitCMAKE_CONFIGURATION_TYPES(std::string const& genDefault)
     return;
   }
   std::string initConfigs;
-  if (!cmSystemTools::GetEnv("CMAKE_CONFIGURATION_TYPES", initConfigs)) {
+  if (this->GetCMakeInstance()->GetIsInTryCompile() ||
+      !cmSystemTools::GetEnv("CMAKE_CONFIGURATION_TYPES", initConfigs)) {
     initConfigs = genDefault;
   }
   this->AddCacheDefinition(

Tests/RunCMake/try_compile/EnvConfig.c

@@ -0,0 +1,7 @@
+#ifdef TC_CONFIG_BAD
+#  error "Built in 'Bad' config"
+#endif
+int main(void)
+{
+  return 0;
+}

Tests/RunCMake/try_compile/EnvConfig.cmake

@@ -0,0 +1,18 @@
+enable_language(C)
+
+set(ENV{CMAKE_BUILD_TYPE} "Bad")
+set(ENV{CMAKE_CONFIGURATION_TYPES} "Bad;Debug")
+
+add_library(tc_defs INTERFACE IMPORTED)
+target_compile_definitions(tc_defs INTERFACE "TC_CONFIG_$<UPPER_CASE:$<CONFIG>>")
+
+try_compile(ENV_CONFIG_RESULT "${CMAKE_BINARY_DIR}"
+  SOURCES "${CMAKE_CURRENT_SOURCE_DIR}/EnvConfig.c"
+  COPY_FILE "${CMAKE_CURRENT_BINARY_DIR}/EnvConfig.bin"
+  OUTPUT_VARIABLE tc_output
+  LINK_LIBRARIES tc_defs
+  )
+if(NOT ENV_CONFIG_RESULT)
+  string(REPLACE "\n" "\n  " tc_output "  ${tc_output}")
+  message(FATAL_ERROR "try_compile failed:\n${tc_output}")
+endif()

Tests/RunCMake/try_compile/RunCMakeTest.cmake

@@ -16,6 +16,8 @@ run_cmake(BadSources2)
 run_cmake(NonSourceCopyFile)
 run_cmake(NonSourceCompileDefinitions)
 
+run_cmake(EnvConfig)
+
 set(RunCMake_TEST_OPTIONS --debug-trycompile)
 run_cmake(PlatformVariables)
 run_cmake(WarnDeprecated)