[Linux] Add build-id support.

Add a `-build-id` option to the driver to let users control the build
ID setting used by the linker.  Pass `--build-id` to the linker by default,
so that build IDs are enabled by default but using the linker's default
type; if someone wishes to specify a particular option, they can do so
using the new driver option.

Also turn on build IDs when *building* the driver.

rdar://116798309

Author: al45tair

CMakeLists.txt

@@ -31,6 +31,12 @@ set(CMAKE_Swift_COMPILE_OPTIONS_MSVC_RUNTIME_LIBRARY MultiThreadedDLL)
 set(CMAKE_Swift_LANGUAGE_VERSION 5)
 set(CMAKE_Swift_MODULE_DIRECTORY ${CMAKE_BINARY_DIR}/swift)
 
+# Generate build-ids
+if(NOT CMAKE_SYSTEM_NAME STREQUAL "Darwin"
+    AND NOT CMAKE_SYSTEM_NAME STREQUAL "Windows")
+  add_link_options("LINKER:--build-id=sha1")
+endif()
+
 # ensure Swift compiler can find _CSwiftScan
 add_compile_options($<$<COMPILE_LANGUAGE:Swift>:-I$<SEMICOLON>${CMAKE_CURRENT_SOURCE_DIR}/Sources/CSwiftScan/include>)
 

Sources/SwiftDriver/Jobs/GenericUnixToolchain+LinkerSupport.swift

@@ -106,6 +106,19 @@ extension GenericUnixToolchain {
         commandLine.appendFlag("-pie")
       }
 
+      // On some platforms we want to enable --build-id
+      if targetTriple.os == .linux
+           || targetTriple.os == .freeBSD
+           || targetTriple.os == .openbsd
+           || parsedOptions.hasArgument(.buildId) {
+        commandLine.appendFlag("-Xlinker")
+        if let buildId = parsedOptions.getLastArgument(.buildId)?.asSingle {
+          commandLine.appendFlag("--build-id=\(buildId)")
+        } else {
+          commandLine.appendFlag("--build-id")
+        }
+      }
+
       let staticStdlib = parsedOptions.hasFlag(positive: .staticStdlib,
                                                negative: .noStaticStdlib,
                                                    default: false)

Sources/SwiftOptions/Options.swift

@@ -58,6 +58,8 @@ extension Option {
   public static let bridgingHeaderDirectoryForPrint: Option = Option("-bridging-header-directory-for-print", .separate, attributes: [.helpHidden, .frontend, .noDriver], metaVar: "<path>", helpText: "Directory for bridging header to be printed in compatibility header")
   public static let bridgingHeaderPchKey: Option = Option("-bridging-header-pch-key", .separate, attributes: [.helpHidden, .frontend, .noDriver], helpText: "Cache Key for bridging header pch")
   public static let bsdk: Option = Option("-bsdk", .joinedOrSeparate, attributes: [.noDriver, .argumentIsPath], helpText: "path to the baseline SDK to import frameworks")
+  public static let buildIdEQ: Option = Option("-build-id=", .joined, alias: Option.buildId)
+  public static let buildId: Option = Option("-build-id", .joinedOrSeparate, metaVar: "<build-id>", helpText: "Specify the build ID argument passed to linker")
   public static let buildModuleFromParseableInterface: Option = Option("-build-module-from-parseable-interface", .flag, alias: Option.compileModuleFromInterface, attributes: [.helpHidden, .frontend, .noDriver], group: .modes)
   public static let bypassBatchModeChecks: Option = Option("-bypass-batch-mode-checks", .flag, attributes: [.helpHidden, .frontend, .noDriver], helpText: "Bypass checks for batch-mode errors.")
   public static let bypassResilience: Option = Option("-bypass-resilience-checks", .flag, attributes: [.helpHidden, .frontend, .noDriver], helpText: "Ignore all checks for module resilience.")
@@ -921,6 +923,8 @@ extension Option {
       Option.bridgingHeaderDirectoryForPrint,
       Option.bridgingHeaderPchKey,
       Option.bsdk,
+      Option.buildIdEQ,
+      Option.buildId,
       Option.buildModuleFromParseableInterface,
       Option.bypassBatchModeChecks,
       Option.bypassResilience,