cmCustomCommandGenerator: Collect genex target references in commands

These will become target-level dependencies.

Source/cmCustomCommandGenerator.cxx

@@ -62,6 +62,10 @@ cmCustomCommandGenerator::cmCustomCommandGenerator(cmCustomCommand const& cc,
     for (std::string const& clarg : cmdline) {
       std::unique_ptr<cmCompiledGeneratorExpression> cge = ge.Parse(clarg);
       std::string parsed_arg = cge->Evaluate(this->LG, this->Config);
+      for (cmGeneratorTarget* gt : cge->GetTargets()) {
+        this->Utilities.emplace(BT<std::pair<std::string, bool>>(
+          { gt->GetName(), true }, cge->GetBacktrace()));
+      }
       if (this->CC->GetCommandExpandLists()) {
         cm::append(argv, cmExpandedList(parsed_arg));
       } else {
@@ -69,10 +73,18 @@ cmCustomCommandGenerator::cmCustomCommandGenerator(cmCustomCommand const& cc,
       }
     }
 
-    // Later code assumes at least one entry exists, but expanding
-    // lists on an empty command may have left this empty.
-    // FIXME: Should we define behavior for removing empty commands?
-    if (argv.empty()) {
+    if (!argv.empty()) {
+      // If the command references an executable target by name,
+      // collect the target to add a target-level dependency on it.
+      cmGeneratorTarget* gt = this->LG->FindGeneratorTargetToUse(argv.front());
+      if (gt && gt->GetType() == cmStateEnums::EXECUTABLE) {
+        this->Utilities.emplace(BT<std::pair<std::string, bool>>(
+          { gt->GetName(), true }, cc.GetBacktrace()));
+      }
+    } else {
+      // Later code assumes at least one entry exists, but expanding
+      // lists on an empty command may have left this empty.
+      // FIXME: Should we define behavior for removing empty commands?
       argv.emplace_back();
     }
 
@@ -326,3 +338,9 @@ std::vector<std::string> const& cmCustomCommandGenerator::GetDepends() const
 {
   return this->Depends;
 }
+
+std::set<BT<std::pair<std::string, bool>>> const&
+cmCustomCommandGenerator::GetUtilities() const
+{
+  return this->Utilities;
+}

Source/cmCustomCommandGenerator.h

@@ -4,10 +4,13 @@
 
 #include "cmConfigure.h" // IWYU pragma: keep
 
+#include <set>
 #include <string>
+#include <utility>
 #include <vector>
 
 #include "cmCustomCommandLines.h"
+#include "cmListFileCache.h"
 
 class cmCustomCommand;
 class cmLocalGenerator;
@@ -24,6 +27,7 @@ class cmCustomCommandGenerator
   std::vector<std::string> Byproducts;
   std::vector<std::string> Depends;
   std::string WorkingDirectory;
+  std::set<BT<std::pair<std::string, bool>>> Utilities;
 
   void FillEmulatorsWithArguments();
   std::vector<std::string> GetCrossCompilingEmulator(unsigned int c) const;
@@ -46,6 +50,7 @@ public:
   std::vector<std::string> const& GetOutputs() const;
   std::vector<std::string> const& GetByproducts() const;
   std::vector<std::string> const& GetDepends() const;
+  std::set<BT<std::pair<std::string, bool>>> const& GetUtilities() const;
   bool HasOnlyEmptyCommandLines() const;
   std::string GetFullDepfile() const;
   std::string GetInternalDepfile() const;