Add support for SWIFTCI_USE_LOCAL_DEPS in swift-inspect

If the `SWIFTCI_USE_LOCAL_DEPS` environment variable is set, we're building in the Swift.org CI system alongside other projects in the Swift toolchain and we can depend on local versions of our dependencies instead of fetching them remotely.

Author: stevapple

tools/swift-inspect/Package.swift

@@ -2,15 +2,13 @@
 // The swift-tools-version declares the minimum version of Swift required to build this package.
 
 import PackageDescription
+import class Foundation.ProcessInfo
 
 let package = Package(
     name: "swift-inspect",
     products: [
         .library(name: "SwiftInspectClient", type: .dynamic, targets: ["SwiftInspectClient"]),
     ],
-    dependencies: [
-        .package(url: "https://github.com/apple/swift-argument-parser", from: "1.2.2"),
-    ],
     targets: [
         // Targets are the basic building blocks of a package. A target can define a module or a test suite.
         // Targets can depend on other targets in this package, and on products in packages which this package depends on.
@@ -36,3 +34,11 @@ let package = Package(
             name: "SymbolicationShims")
     ]
 )
+
+if ProcessInfo.processInfo.environment["SWIFTCI_USE_LOCAL_DEPS"] == nil {
+    package.dependencies += [
+        .package(url: "https://github.com/apple/swift-argument-parser.git", from: "1.2.2"),
+    ]
+} else {
+    package.dependencies += [.package(path: "../../../swift-argument-parser")]
+}

utils/build.ps1

@@ -1530,12 +1530,14 @@ function Install-HostToolchain() {
 function Build-Inspect() {
   $OutDir = Join-Path -Path $HostArch.BinaryCache -ChildPath swift-inspect
 
-  Build-SPMProject `
-    -Src $SourceCache\swift\tools\swift-inspect `
-    -Bin $OutDir `
-    -Arch $HostArch `
-    -Xcc "-I$SDKInstallRoot\usr\include\swift\SwiftRemoteMirror" -Xlinker "$SDKInstallRoot\usr\lib\swift\windows\$($HostArch.LLVMName)\swiftRemoteMirror.lib" `
-    -Xcc -Xclang -Xcc -fno-split-cold-code # Workaround https://github.com/llvm/llvm-project/issues/40056
+  Isolate-EnvVars {
+    $env:SWIFTCI_USE_LOCAL_DEPS=1
+    Build-SPMProject `
+      -Src $SourceCache\swift\tools\swift-inspect `
+      -Bin $OutDir `
+      -Arch $HostArch `
+      -Xcc "-I$SDKInstallRoot\usr\include\swift\SwiftRemoteMirror" -Xlinker "$SDKInstallRoot\usr\lib\swift\windows\$($HostArch.LLVMName)\swiftRemoteMirror.lib"
+  }
 }
 
 function Build-Format() {