Fix linking error on linux

- libstdc++ needs to be added when linking if any dependency has a cpp
  dependency

Author: daveinglis

Sources/SwiftBuildSupport/PackagePIFProjectBuilder+Modules.swift

@@ -499,9 +499,9 @@ extension PackagePIFProjectBuilder {
             for platform in ProjectModel.BuildSettings.Platform.allCases {
                 // darwin & freebsd
                 if [.macOS, .macCatalyst, .iOS, .watchOS, .tvOS, .xrOS, .driverKit, .freebsd].contains(platform) {
-                    settings[.OTHER_LDFLAGS, platform] = ["-lc++", "$(inherited)"]
+                    impartedSettings[.OTHER_LDFLAGS, platform] = ["-lc++", "$(inherited)"]
                 } else if [.android, .linux, .wasi, .openbsd].contains(platform) {
-                    settings[.OTHER_LDFLAGS, platform] = ["-lstdc++", "$(inherited)"]
+                    impartedSettings[.OTHER_LDFLAGS, platform] = ["-lstdc++", "$(inherited)"]
                 }
             }
         }

Tests/SwiftBuildSupportTests/PIFBuilderTests.swift

@@ -163,7 +163,7 @@ struct PIFBuilderTests {
                 .buildConfig(named: "Release")
 
             for platform in ProjectModel.BuildSettings.Platform.allCases {
-                let ld_flags = releaseConfig.settings[.OTHER_LDFLAGS, platform]
+                let ld_flags = releaseConfig.impartedBuildProperties.settings[.OTHER_LDFLAGS, platform]
                 if [.macOS, .macCatalyst, .iOS, .watchOS, .tvOS, .xrOS, .driverKit, .freebsd].contains(platform) {
                      #expect(ld_flags == ["-lc++", "$(inherited)"], "for platform \(platform)")
                 } else if [.android, .linux, .wasi, .openbsd].contains(platform) {