diff --git a/BUILD.gn b/BUILD.gn
index 4c818a3..8b03250 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1,12 +1,13 @@
 import("//build/image/hypervisor.gni")
 
-group("host_tools") {
+group("arch_images") {
   deps = [
     ":hafnium($arch_toolchain)",
   ]
 }
 
 executable("test") {
+  testonly = true
   sources = [
     "test.cpp",
   ]
diff --git a/build/toolchain/arch/BUILD.gn b/build/toolchain/arch/BUILD.gn
index f85c3af..6523339 100644
--- a/build/toolchain/arch/BUILD.gn
+++ b/build/toolchain/arch/BUILD.gn
@@ -76,7 +76,7 @@
 
   cc_toolchain(target_name) {
     cc = "clang"
-    cflags = "-target ${invoker.target}"
+    cflags = "-target ${invoker.target} -fcolor-diagnostics"
     ld = "${invoker.arch_tool_prefix}ld"
 
     toolchain_args = {
@@ -90,6 +90,7 @@
 
   cc_toolchain(target_name) {
     cc = "${invoker.arch_tool_prefix}gcc"
+    cflags = "-fdiagnostics-color=always"
     ld = "${invoker.arch_tool_prefix}ld"
 
     toolchain_args = {
diff --git a/build/toolchain/host/BUILD.gn b/build/toolchain/host/BUILD.gn
index 0c4e52e..76db0e6 100644
--- a/build/toolchain/host/BUILD.gn
+++ b/build/toolchain/host/BUILD.gn
@@ -5,9 +5,16 @@
     assert(defined(invoker.cc), "cc_toolchain() must specify a \"cc\" value")
     assert(defined(invoker.cxx), "cc_toolchain() must specify a \"cxx\" value")
 
+    cc = "${invoker.cc}"
+    cxx = "${invoker.cxx}"
+    if (defined(invoker.cflags)) {
+      cc += " ${invoker.cflags}"
+      cxx += " ${invoker.cflags}"
+    }
+
     tool("cc") {
       depfile = "{{output}}.d"
-      command = "${invoker.cc} -MMD -MF $depfile {{defines}} {{include_dirs}} {{cflags}} {{cflags_c}} -c {{source}} -o {{output}}"
+      command = "${cc} -MMD -MF $depfile {{defines}} {{include_dirs}} {{cflags}} {{cflags_c}} -c {{source}} -o {{output}}"
       depsformat = "gcc"
       description = "CC {{output}}"
       outputs = [
@@ -17,7 +24,7 @@
 
     tool("cxx") {
       depfile = "{{output}}.d"
-      command = "${invoker.cxx} -MMD -MF $depfile {{defines}} {{include_dirs}} {{cflags}} {{cflags_cc}} -c {{source}} -o {{output}}"
+      command = "${cxx} -MMD -MF $depfile {{defines}} {{include_dirs}} {{cflags}} {{cflags_cc}} -c {{source}} -o {{output}}"
       depsformat = "gcc"
       description = "CXX {{output}}"
       outputs = [
@@ -42,7 +49,7 @@
       sofile = "{{output_dir}}/$soname"
       rspfile = soname + ".rsp"
 
-      command = "${invoker.cxx} -shared {{ldflags}} -o $sofile -Wl,-soname=$soname @$rspfile"
+      command = "${cxx} -shared {{ldflags}} -o $sofile -Wl,-soname=$soname @$rspfile"
       rspfile_content = "-Wl,--whole-archive {{inputs}} {{solibs}} -Wl,--no-whole-archive {{libs}}"
 
       description = "SOLINK $soname"
@@ -67,7 +74,7 @@
     tool("link") {
       outfile = "{{output_dir}}/{{target_output_name}}{{output_extension}}"
       rspfile = "$outfile.rsp"
-      command = "${invoker.cxx} {{ldflags}} -o $outfile -Wl,--start-group @$rspfile {{solibs}} -Wl,--end-group {{libs}}"
+      command = "${cxx} {{ldflags}} -o $outfile -Wl,--start-group @$rspfile {{solibs}} -Wl,--end-group {{libs}}"
       description = "LINK $outfile"
       default_output_dir = "{{root_out_dir}}"
       rspfile_content = "{{inputs}}"
@@ -93,10 +100,12 @@
   ar = "llvm-ar"
   cc = "clang"
   cxx = "clang++"
+  cflags = "-fcolor-diagnostics"
 }
 
 cc_toolchain("gcc") {
   ar = "ar"
   cc = "gcc"
   cxx = "g++"
+  cflags = "-fdiagnostics-color=always"
 }