fixup IRGen test for exp on linux

Author: stephentyrone

test/IRGen/builtin_math.swift

@@ -13,13 +13,7 @@
 // Make sure we use an intrinsic for functions such as exp.
 
 // CHECK-LABEL: define {{.*}}test1
-// CHECK-ios: call float @llvm.exp.f32
-// CHECK-macosx: call float @llvm.exp.f32
-// CHECK-tvos: call float @llvm.exp.f32
-// CHECK-watchos: call float @llvm.exp.f32
-// CHECK-darwin: call float @llvm.exp.f32
-// CHECK-linux-gnu: call float @expf
-// CHECK-windows: call float @expf
+// CHECK: call float @llvm.exp.f32
 
 public func test1(f : Float) -> Float {
   return exp(f)