stage2: clarify logic of passing -integrated-as to clang

make it clear that the logic is only there to lower the amount of
noise on the clang command line.

src/Compilation.zig

@@ -2695,9 +2695,7 @@ pub fn addCCArgs(
         try argv.appendSlice(&[_][]const u8{ "-MD", "-MV", "-MF", p });
     }
 
-    if (target.cpu.arch.isSPARC()) {
-        // Clang defaults to using the system assembler over the internal one
-        // when targeting a non-BSD OS.
+    if (target_util.clangMightShellOutForAssembly(target)) {
         try argv.append("-integrated-as");
     }
 

src/target.zig

@@ -395,3 +395,9 @@ pub fn libcFullLinkFlags(target: std.Target) []const []const u8 {
         },
     };
 }
+
+pub fn clangMightShellOutForAssembly(target: std.Target) bool {
+    // Clang defaults to using the system assembler over the internal one
+    // when targeting a non-BSD OS.
+    return target.cpu.arch.isSPARC();
+}