Include String+Bridging.swift in CMakeLists.txt (#1136)

Author: cthielen

Sources/FoundationEssentials/String/CMakeLists.txt

@@ -16,6 +16,7 @@ target_sources(FoundationEssentials PRIVATE
     BidirectionalCollection.swift
     BuiltInUnicodeScalarSet.swift
     RegexPatternCache.swift
+    String+Bridging.swift
     String+Comparison.swift
     String+Encoding.swift
     String+EndianAdaptorSequence.swift