Don't use sanitized kati when SANITIZE_HOST=address is set

There used to be CI builds that set SANITIZE_HOST=address, so we
took advantage of that to also run a sanitize version of kati and
ninja.  Those CI builds are no longer active.

Building host fuzzers requires setting SANITIZE_HOST=address, and
sanitized kati is too slow to use for developer builds.  Split out
a separate SANITIZE_BUILD_TOOL_PREBUILTS flag that can be set when
manual testing of sanitized host tool prebuilts is desired.

SANTIIZE_HOST=address will still affect any tools that are built
during the build.

Change-Id: Ifc85d50655aa05e5f0784370086c7203162c8158
Fixes: 278603593
Flag: EXEMPT host-only
Test: manual
diff --git a/ui/build/config.go b/ui/build/config.go
index bd20442..75edfcd 100644
--- a/ui/build/config.go
+++ b/ui/build/config.go
@@ -1754,12 +1754,10 @@
 }
 
 func (c *configImpl) PrebuiltBuildTool(name string) string {
-	if v, ok := c.environ.Get("SANITIZE_HOST"); ok {
-		if sanitize := strings.Fields(v); inList("address", sanitize) {
-			asan := filepath.Join("prebuilts/build-tools", c.HostPrebuiltTag(), "asan/bin", name)
-			if _, err := os.Stat(asan); err == nil {
-				return asan
-			}
+	if c.environ.IsEnvTrue("SANITIZE_BUILD_TOOL_PREBUILTS") {
+		asan := filepath.Join("prebuilts/build-tools", c.HostPrebuiltTag(), "asan/bin", name)
+		if _, err := os.Stat(asan); err == nil {
+			return asan
 		}
 	}
 	return filepath.Join("prebuilts/build-tools", c.HostPrebuiltTag(), "bin", name)