Add readelf and nm dummy values to cros.

build/toolchain/gcc_toolchain.gni

Index: build/toolchain/gcc_toolchain.gni
diff --git a/build/toolchain/gcc_toolchain.gni b/build/toolchain/gcc_toolchain.gni
index 3421a9575bda75ed497f57cf2ec3b7e8b3587123..29b913759653962261e3e3d585c30dee95e2fa07 100644
--- a/build/toolchain/gcc_toolchain.gni
+++ b/build/toolchain/gcc_toolchain.gni
@@ -13,8 +13,6 @@ concurrent_links = exec_script("get_concurrent_links.py", [], "value")
 #  - cxx
 #  - ar
 #  - ld
-#  - readelf
-#  - nm
 # and the following which is used in the toolchain_args
 #  - toolchain_cpu  (What "current_cpu" should be set to when invoking a
 #                    build using this toolchain.)
@@ -42,9 +40,6 @@ template("gcc_toolchain") {
     assert(defined(invoker.cxx), "gcc_toolchain() must specify a \"cxx\" value")
     assert(defined(invoker.ar), "gcc_toolchain() must specify a \"ar\" value")
     assert(defined(invoker.ld), "gcc_toolchain() must specify a \"ld\" value")
-    assert(defined(invoker.readelf),
-           "gcc_toolchain() must specify a \"readelf\" value")
-    assert(defined(invoker.nm), "gcc_toolchain() must specify a \"nm\" value")
     assert(defined(invoker.toolchain_cpu),
            "gcc_toolchain() must specify a \"toolchain_cpu\"")
     assert(defined(invoker.toolchain_os),
@@ -57,8 +52,16 @@ template("gcc_toolchain") {
     cxx = invoker.cxx
     ar = invoker.ar
     ld = invoker.ld
-    readelf = invoker.readelf
-    nm = invoker.nm
+    if (defined(invoker.readelf)) {
+      readelf = invoker.readelf
+    } else {
+      readelf = "readelf"
+    }
+    if (defined(invoker.nm)) {
+      nm = invoker.nm
+    } else {
+      nm = "nm"
+    }
 
     # Bring these into our scope for string interpolation with default values.
     if (defined(invoker.libs_section_prefix)) {
@@ -145,6 +148,8 @@ template("gcc_toolchain") {
       temporary_tocname = sofile + ".tmp"
       link_command =
           "$ld -shared {{ldflags}} -o $sofile -Wl,-soname=$soname @$rspfile"
+      assert(defined(readelf), "to solink you must have a readelf")
+      assert(defined(nm), "to solink you must have an nm")
       toc_command = "{ $readelf -d $sofile | grep SONAME ; $nm -gD -f p $sofile | cut -f1-2 -d' '; } > $temporary_tocname"
       replace_command = "if ! cmp -s $temporary_tocname $tocfile; then mv $temporary_tocname $tocfile; fi"