[infra] Assembles the SDK using GN rather than create_sdk.py

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 11753343accb33652dba166c83363c7899ce86ae..1cbdb5f8c5d2520ad8fc4d141a75da883d35dbb9 100644
--- a/build/toolchain/gcc_toolchain.gni
+++ b/build/toolchain/gcc_toolchain.gni
@@ -38,8 +38,8 @@ concurrent_links = exec_script("get_concurrent_links.py", [], "value")
 #  - is_clang
 #  - strip
 #      Location of the strip executable. When specified, strip will be run on
-#      all shared libraries and executables as they are built. The pre-stripped
-#      artifacts will be put in lib.stripped/ and exe.stripped/.
+#      all executables as they are built. The stripped artifacts will be put in
+#      exe.stripped/.
 template("gcc_toolchain") {
   toolchain(target_name) {
     assert(defined(invoker.cc), "gcc_toolchain() must specify a \"cc\" value")
@@ -192,17 +192,16 @@ template("gcc_toolchain") {
       exename = "{{target_output_name}}{{output_extension}}"
       outfile = "{{root_out_dir}}/$exename"
       rspfile = "$outfile.rsp"
-      unstripped_outfile = outfile
 
       if (defined(invoker.strip)) {
-        unstripped_outfile = "{{root_out_dir}}/exe.unstripped/$exename"
+        stripped_outfile = "{{root_out_dir}}/exe.stripped/$exename"
       }
 
-      command = "$ld {{ldflags}} -o $unstripped_outfile -Wl,--start-group @$rspfile {{solibs}} -Wl,--end-group $libs_section_prefix {{libs}} $libs_section_postfix"
+      command = "$ld {{ldflags}} -o $outfile -Wl,--start-group @$rspfile {{solibs}} -Wl,--end-group $libs_section_prefix {{libs}} $libs_section_postfix"
       if (defined(invoker.strip)) {
         strip = invoker.strip
         strip_command =
-            "${strip} --strip-unneeded -o $outfile $unstripped_outfile"
+            "${strip} --strip-unneeded -o $stripped_outfile $outfile"
         command += " && " + strip_command
       }
       if (defined(invoker.postlink)) {
@@ -213,8 +212,8 @@ template("gcc_toolchain") {
       outputs = [
         outfile,
       ]
-      if (outfile != unstripped_outfile) {
-        outputs += [ unstripped_outfile ]
+      if (defined(invoker.strip)) {
+        outputs += [ stripped_outfile ]
       }
       if (defined(invoker.link_outputs)) {
         outputs += invoker.link_outputs