target_link_libraries: Fix regression in case of $<CONFIG> genex

Since commit b8626261e9 (Precompile headers: Add methods to generate PCH
sources, 2019-07-13, v3.16.0-rc1~182^2~4) we look up source files for a
target using an upper-case configuration even though an original-case
name is sufficient.  Since commit 36ded610af (PCH: Generate sources
during Compute step, 2019-10-05, v3.16.0-rc1~2^2) the source file lookup
is the first time we compute many on-demand structures that depend on
the configuration name.  This caused the `$<CONFIG>` generator
expression to evaluate to the upper-case configuration name in some
cases where we used original-case before.

Fix this by switching the source file lookup to the original-case config
name.  Add a test covering the symptom that led to the discovery of this
problem.

Fixes: #20517

1 files changed, 2 insertions, 5 deletions

diff --git a/Source/cmLocalGenerator.cxx b/Source/cmLocalGenerator.cxx
index ffd46d4..af92e1b 100644
--- a/Source/cmLocalGenerator.cxx
+++ b/Source/cmLocalGenerator.cxx
@@ -2306,11 +2306,10 @@ void cmLocalGenerator::AddPchDependencies(cmGeneratorTarget* target)
   if (!this->GetGlobalGenerator()->IsMultiConfig()) {
     config = this->Makefile->GetSafeDefinition("CMAKE_BUILD_TYPE");
   }
-  const std::string buildType = cmSystemTools::UpperCase(config);
 
   // FIXME: Refactor collection of sources to not evaluate object libraries.
   std::vector<cmSourceFile*> sources;
-  target->GetSourceFiles(sources, buildType);
+  target->GetSourceFiles(sources, config);
 
   for (const std::string& lang : { "C", "CXX", "OBJC", "OBJCXX" }) {
     auto langSources =
@@ -2481,15 +2480,13 @@ void cmLocalGenerator::AddUnityBuild(cmGeneratorTarget* target)
     config = this->Makefile->GetSafeDefinition("CMAKE_BUILD_TYPE");
   }
 
-  const std::string buildType = cmSystemTools::UpperCase(config);
-
   std::string filename_base =
     cmStrCat(this->GetCurrentBinaryDirectory(), "/CMakeFiles/",
              target->GetName(), ".dir/Unity/");
 
   // FIXME: Refactor collection of sources to not evaluate object libraries.
   std::vector<cmSourceFile*> sources;
-  target->GetSourceFiles(sources, buildType);
+  target->GetSourceFiles(sources, config);
 
   auto batchSizeString = target->GetProperty("UNITY_BUILD_BATCH_SIZE");
   const size_t unityBatchSize =