internal/rosa: global preset flags

These changes preset behaviour globally. Useful for ad hoc workarounds for development or bootstrapping on resource-constrained systems.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/rosa/llvm.go

@@ -90,10 +90,14 @@ func (t Toolchain) newLLVM() (pkg.Artifact, string) {
 			skipChecks[i] = s
 		}
 
-		cache = append(cache, []KV{
-			// very expensive
-			{"LLVM_ENABLE_LTO", "Thin"},
+		if presetOpts&OptLLVMNoLTO == 0 {
+			cache = append(cache, []KV{
+				// very expensive
+				{"LLVM_ENABLE_LTO", "Thin"},
+			}...)
+		}
 
+		cache = append(cache, []KV{
 			// symbols: clock_gettime, mallopt
 			{"COMPILER_RT_INCLUDE_TESTS", "OFF"},