Fix the build on Linux

Motivation:

A number of the changes in the code for running on Linux
were not validated ahead of time, and broke the build.

Modifications:

- Correct the spelling of Glibc
- Modified string initialization on non-Darwin platforms

Results:

Builds and passes tests on Linux

Author: Lukasa

Sources/StructuredHeaders/FieldParser.swift

@@ -522,14 +522,25 @@ extension String {
         // We assume the string is previously validated, so the escapes are easily removed. See the doc comment for
         // `StrippingStringEscapesCollection` for more details on what we're doing here.
         let unescapedBytes = StrippingStringEscapesCollection(bytes, escapes: escapes)
-        if #available(macOS 10.16, macCatalyst 10.16, iOS 14.0, watchOS 7.0, tvOS 14.0, *) {
-            return String(unsafeUninitializedCapacity: unescapedBytes.count) { innerPtr in
-                let (_, endIndex) = innerPtr.initialize(from: unescapedBytes)
-                return endIndex
+        #if canImport(Darwin)
+            if #available(macOS 10.16, macCatalyst 10.16, iOS 14.0, watchOS 7.0, tvOS 14.0, *) {
+                return String(unsafeUninitializedCapacity: unescapedBytes.count) { innerPtr in
+                    let (_, endIndex) = innerPtr.initialize(from: unescapedBytes)
+                    return endIndex
+                }
+            } else {
+                return String(decoding: unescapedBytes, as: UTF8.self)
             }
-        } else {
-            return String(decoding: unescapedBytes, as: UTF8.self)
-        }
+         #else
+             #if compiler(>=5.3)
+                return String(unsafeUninitializedCapacity: unescapedBytes.count) { innerPtr in
+                    let (_, endIndex) = innerPtr.initialize(from: unescapedBytes)
+                    return endIndex
+                }
+             #else
+                return String(decoding: unescapedBytes, as: UTF8.self)
+             #endif
+         #endif
     }
 }
 

Sources/StructuredHeaders/PseudoDecimal.swift

@@ -13,8 +13,8 @@
 //===----------------------------------------------------------------------===//
 #if canImport(Darwin)
 import Darwin
-#elseif canImport(GLibc)
-import GLibc
+#elseif canImport(Glibc)
+import Glibc
 #else
 #error("Unsupported OS")
 #endif