[gn build] Port fb458aa

Author: llvmgnsyncbot

llvm/utils/gn/secondary/llvm/lib/Support/BUILD.gn

@@ -103,6 +103,7 @@ static_library("Support") {
     "IntEqClasses.cpp",
     "IntervalMap.cpp",
     "JSON.cpp",
+    "Jobserver.cpp",
     "KnownBits.cpp",
     "KnownFPClass.cpp",
     "LEB128.cpp",

llvm/utils/gn/secondary/llvm/unittests/Support/BUILD.gn

@@ -56,6 +56,7 @@ unittest("SupportTests") {
     "InstructionCostTest.cpp",
     "InterleavedRangeTest.cpp",
     "JSONTest.cpp",
+    "JobserverTest.cpp",
     "KnownBitsTest.cpp",
     "LEB128Test.cpp",
     "LineIteratorTest.cpp",