Merge pull request compiler-explorer#1808 from Azoy/patch-2

Add Swift nightly builds

Author: mattgodbolt

etc/config/swift.amazon.properties

@@ -2,7 +2,7 @@ compilers=&swift
 demangler=/opt/compiler-explorer/swift-5.1/usr/bin/swift-demangle
 defaultCompiler=swift51
 
-group.swift.compilers=swift311:swift402:swift403:swift41:swift411:swift412:swift42:swift50:swift51
+group.swift.compilers=swift311:swift402:swift403:swift41:swift411:swift412:swift42:swift50:swift51:swiftnightly
 group.swift.isSemVer=true
 group.swift.baseName=x86-64 swiftc
 compiler.swift311.exe=/opt/compiler-explorer/swift-3.1.1/usr/bin/swiftc
@@ -23,7 +23,8 @@ compiler.swift50.exe=/opt/compiler-explorer/swift-5.0/usr/bin/swiftc
 compiler.swift50.semver=5.0
 compiler.swift51.exe=/opt/compiler-explorer/swift-5.1/usr/bin/swiftc
 compiler.swift51.semver=5.1
-
+compiler.swiftnightly.exe=/opt/compiler-explorer/swift-nightly/usr/bin/swiftc
+compiler.swiftnightly.semver=nightly
 
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