Make sure that the command for a plugin-generated command is unique by including the command line as well. (#3585)

Otherwise the llbuild manifest will contain only the last defined command with the same name, leading to build failures.

To avoid having the name be exceedingly long, what we append to the name is a digest of the command line and not the full command line itself.

rdar://79872414

Author: abertelrud

Fixtures/Miscellaneous/Plugins/ContrivedTestPlugin/Package.swift

@@ -9,6 +9,7 @@ let package = Package(
             name: "MyLocalTool",
             plugins: [
                 "MySourceGenBuildToolPlugin",
+                "MyAmbiguouslyNamedCommandPlugin",
             ]
         ),
         // The plugin that generates build tool commands to invoke MySourceGenBuildTool.
@@ -23,5 +24,13 @@ let package = Package(
         .executableTarget(
             name: "MySourceGenBuildTool"
         ),
+        // Plugin that emits commands with a generic name.
+        .plugin(
+            name: "MyAmbiguouslyNamedCommandPlugin",
+            capability: .buildTool(),
+            dependencies: [
+                "MySourceGenBuildTool",
+            ]
+        ),
     ]
 )

Fixtures/Miscellaneous/Plugins/ContrivedTestPlugin/Plugins/MyAmbiguouslyNamedCommandPlugin/plugin.swift

@@ -0,0 +1,26 @@
+import PackagePlugin
+ 
+for inputFile in targetBuildContext.inputFiles.filter({ $0.path.extension == "dat" }) {
+    let inputPath = inputFile.path
+    let outputName = "Ambiguous_" + inputPath.stem + ".swift"
+    let outputPath = targetBuildContext.pluginWorkDirectory.appending(outputName)
+    commandConstructor.addBuildCommand(
+        displayName:
+            "This is a constant name",
+        executable:
+            try targetBuildContext.tool(named: "MySourceGenBuildTool").path,
+        arguments: [
+            "\(inputPath)",
+            "\(outputPath)"
+        ],
+        environment: [
+            "VARIABLE_NAME_PREFIX": "SECOND_PREFIX_"
+        ],
+        inputFiles: [
+            inputPath,
+        ],
+        outputFiles: [
+            outputPath
+        ]
+    )
+}

Fixtures/Miscellaneous/Plugins/ContrivedTestPlugin/Sources/MyLocalTool/bar.dat

@@ -0,0 +1 @@
+I am Bar!

Sources/Build/ManifestBuilder.swift

@@ -584,10 +584,11 @@ extension LLBuildManifestBuilder {
 
         // Add any regular build commands created by plugins for the target (prebuild commands are handled separately).
         for command in target.pluginInvocationResults.reduce([], { $0 + $1.buildCommands }) {
-            // Create a shell command to invoke the executable. We include the path of the executable as a dependency.
+            // Create a shell command to invoke the executable. We include the path of the executable as a dependency, and make sure the name is unique.
             let execPath = AbsolutePath(command.configuration.executable, relativeTo: buildParameters.buildPath)
+            let uniquedName = ([execPath.pathString] + command.configuration.arguments).joined(separator: "|")
             manifest.addShellCmd(
-                name: command.configuration.displayName,
+                name: command.configuration.displayName + "-" + ByteString(encodingAsUTF8: uniquedName).sha256Checksum,
                 description: command.configuration.displayName,
                 inputs: [.file(execPath)] + command.inputFiles.map{ .file($0) },
                 outputs: command.outputFiles.map{ .file($0) },