Install macOS helper from PKG for XPC enroll

Browser enrollment used osascript on every elevate. Ship a signed
privileged helper installed at PKG time so probo:// can enroll over
XPC with no second admin prompt. Add make install/uninstall/clean for
local PKG test loops, and show alerts only on failure.

Mirror the Go lint path for the macOS SPM package: Make
targets, root configs, and a Linux CI job. Keep checks
syntax-only so they do not need a macOS SDK. Format the
existing sources so the new gates start clean.

Signed-off-by: Ludovic Vielle <ludovic@probo.com>

cmd/probo-agent/installer/macos/enroll-ui/Package.swift

@@ -4,11 +4,43 @@ import PackageDescription
 let package = Package(
     name: "probo-agent-url-handler",
     platforms: [
-        .macOS(.v11),
+        .macOS(.v11)
+    ],
+    products: [
+        .library(name: "ProboAgentShared", targets: ["ProboAgentShared"]),
+        .library(name: "HelperClient", targets: ["HelperClient"]),
+        .executable(name: "com.probo.agent.helper", targets: ["com.probo.agent.helper"]),
+        .executable(name: "probo-agent-url-handler", targets: ["probo-agent-url-handler"]),
     ],
     targets: [
+        .target(
+            name: "ProboAgentShared",
+            path: "Shared",
+            exclude: [
+                "HelperVersion.generated.swift.tmpl",
+                "SigningConstants.generated.swift.tmpl",
+            ],
+            linkerSettings: [
+                .linkedFramework("Security")
+            ]
+        ),
+        .target(
+            name: "HelperClient",
+            dependencies: ["ProboAgentShared"],
+            path: "HelperClient"
+        ),
+        .executableTarget(
+            name: "com.probo.agent.helper",
+            dependencies: ["ProboAgentShared"],
+            path: "HelperTool",
+            exclude: ["Info.plist.tmpl", "Launchd.plist.tmpl"],
+            linkerSettings: [
+                .linkedFramework("Security")
+            ]
+        ),
         .executableTarget(
             name: "probo-agent-url-handler",
+            dependencies: ["HelperClient", "ProboAgentShared"],
             path: "URLHandlerSources"
         ),
     ]