[PackageDescription] Remove underscore from build settings APIs

<rdar://problem/23270646> [SR-3948] Need support for specifying build settings

Author: aciidgh

Sources/PackageDescription4/Target.swift

@@ -81,16 +81,16 @@ public final class Target {
     public let providers: [SystemPackageProvider]?
 
     /// C build settings.
-    var cSettings: [CSetting]?
+    public var cSettings: [CSetting]?
 
     /// C++ build settings.
-    var cxxSettings: [CXXSetting]?
+    public var cxxSettings: [CXXSetting]?
 
     /// Swift build settings.
-    var swiftSettings: [SwiftSetting]?
+    public var swiftSettings: [SwiftSetting]?
 
     /// Linker build settings.
-    var linkerSettings: [LinkerSetting]?
+    public var linkerSettings: [LinkerSetting]?
 
     /// Construct a target.
     private init(
@@ -136,10 +136,10 @@ public final class Target {
         exclude: [String] = [],
         sources: [String]? = nil,
         publicHeadersPath: String? = nil,
-        _cSettings: [CSetting]? = nil,
-        _cxxSettings: [CXXSetting]? = nil,
-        _swiftSettings: [SwiftSetting]? = nil,
-        _linkerSettings: [LinkerSetting]? = nil
+        cSettings: [CSetting]? = nil,
+        cxxSettings: [CXXSetting]? = nil,
+        swiftSettings: [SwiftSetting]? = nil,
+        linkerSettings: [LinkerSetting]? = nil
     ) -> Target {
         return Target(
             name: name,
@@ -149,10 +149,10 @@ public final class Target {
             sources: sources,
             publicHeadersPath: publicHeadersPath,
             type: .regular,
-            cSettings: _cSettings,
-            cxxSettings: _cxxSettings,
-            swiftSettings: _swiftSettings,
-            linkerSettings: _linkerSettings
+            cSettings: cSettings,
+            cxxSettings: cxxSettings,
+            swiftSettings: swiftSettings,
+            linkerSettings: linkerSettings
         )
     }
 
@@ -162,10 +162,10 @@ public final class Target {
         path: String? = nil,
         exclude: [String] = [],
         sources: [String]? = nil,
-        _cSettings: [CSetting]? = nil,
-        _cxxSettings: [CXXSetting]? = nil,
-        _swiftSettings: [SwiftSetting]? = nil,
-        _linkerSettings: [LinkerSetting]? = nil
+        cSettings: [CSetting]? = nil,
+        cxxSettings: [CXXSetting]? = nil,
+        swiftSettings: [SwiftSetting]? = nil,
+        linkerSettings: [LinkerSetting]? = nil
     ) -> Target {
         return Target(
             name: name,
@@ -175,10 +175,10 @@ public final class Target {
             sources: sources,
             publicHeadersPath: nil,
             type: .test,
-            cSettings: _cSettings,
-            cxxSettings: _cxxSettings,
-            swiftSettings: _swiftSettings,
-            linkerSettings: _linkerSettings
+            cSettings: cSettings,
+            cxxSettings: cxxSettings,
+            swiftSettings: swiftSettings,
+            linkerSettings: linkerSettings
         )
     }
 

Tests/PackageLoadingTests/PD4_2LoadingTests.swift

@@ -229,10 +229,10 @@ class PackageDescription4_2LoadingTests: XCTestCase {
                targets: [
                    .target(
                        name: "Foo",
-                       _swiftSettings: [
+                       swiftSettings: [
                            .define("SWIFT", .when(configuration: .release)),
                        ],
-                       _linkerSettings: [
+                       linkerSettings: [
                            .linkedLibrary("libz"),
                        ]
                    ),

Tests/PackageLoadingTests/PD5LoadingTests.swift

@@ -236,20 +236,20 @@ class PackageDescription5LoadingTests: XCTestCase {
                targets: [
                    .target(
                        name: "Foo",
-                       _cSettings: [
+                       cSettings: [
                            .headerSearchPath("path/to/foo"),
                            .define("C", .when(platforms: [.linux])),
                            .define("CC", to: "4", .when(platforms: [.linux], configuration: .release)),
                        ],
-                       _cxxSettings: [
+                       cxxSettings: [
                            .headerSearchPath("path/to/bar"),
                            .define("CXX"),
                        ],
-                       _swiftSettings: [
+                       swiftSettings: [
                            .define("SWIFT", .when(configuration: .release)),
                            .define("SWIFT_DEBUG", .when(platforms: [.watchOS], configuration: .debug)),
                        ],
-                       _linkerSettings: [
+                       linkerSettings: [
                            .linkedLibrary("libz"),
                            .linkedFramework("CoreData", .when(platforms: [.macOS, .tvOS])),
                        ]