build: move libcc patches to electron repo (#14104)

In the GN build, libchromiumcontent is no longer a distinct library, but
merely a container for a set of scripts and patches. Maintaining those
patches in a separate repository is tedious and error-prone, so merge
them into the main repo.

Once this is merged and GN is the default way to build Electron, the
libchromiumcontent repository can be archived.

patches/common/chromium/boringssl_build_gn.patch

@@ -0,0 +1,18 @@
+diff --git a/third_party/boringssl/BUILD.gn b/third_party/boringssl/BUILD.gn
+index c75fb7c2bb7e..423f4b2ddb10 100644
+--- a/third_party/boringssl/BUILD.gn
++++ b/third_party/boringssl/BUILD.gn
+@@ -44,6 +44,13 @@ config("no_asm_config") {
+ }
+ 
+ all_sources = crypto_sources + ssl_sources
++if (is_electron_build) {
++  # Needed to build a nodejs-compatible boringssl.
++  all_sources += [
++    "src/decrepit/evp/evp_do_all.c",
++    "src/decrepit/xts/xts.c",
++  ]
++}
+ 
+ # Windows' assembly is built with Yasm. The other platforms use the platform
+ # assembler.