Get FoundationInternationalization building

Adding the missing Musl imports to get FoundationInternationalization
building for the static SDK.

Author: etcwilde

Sources/FoundationInternationalization/Calendar/Calendar_ICU.swift

@@ -18,6 +18,8 @@ import FoundationEssentials
 import Android
 #elseif canImport(Glibc)
 import Glibc
+#elseif canImport(Musl)
+import Musl
 #elseif canImport(CRT)
 import CRT
 #elseif canImport(Darwin)

Sources/FoundationInternationalization/Date+ICU.swift

@@ -19,6 +19,8 @@ internal import _FoundationICU
 import Android
 #elseif canImport(Glibc)
 import Glibc
+#elseif canImport(Musl)
+import Musl
 #elseif canImport(Darwin)
 import Darwin
 #endif

Sources/FoundationInternationalization/Formatting/Date/ICUDateFormatter.swift

@@ -22,6 +22,8 @@ import Darwin
 import Android
 #elseif canImport(Glibc)
 import Glibc
+#elseif canImport(Musl)
+import Musl
 #endif
 
 typealias UChar = UInt16

Sources/FoundationInternationalization/Formatting/Duration+Formatting.swift

@@ -20,6 +20,8 @@ import Darwin
 import Android
 #elseif canImport(Glibc)
 import Glibc
+#elseif canImport(Musl)
+import Musl
 #elseif os(Windows)
 import CRT
 #elseif os(WASI)