Description: point clang to the toolchain provided by the gcc-mozilla package (version 7 required for C++ 17), and statically link against libstdc++
Author: Olivier Tilloy <olivier.tilloy@canonical.com>
Bug-Ubuntu: https://launchpad.net/bugs/1856861

--- a/build/moz.configure/toolchain.configure
+++ b/build/moz.configure/toolchain.configure
@@ -1252,6 +1252,7 @@ try_compile(includes=['cstddef'],
             "#endif",
         ]
     ),
+    flags=["--gcc-toolchain=/usr/lib/gcc-mozilla"],
     check_msg="for new enough STL headers from libstdc++",
     when=needs_libstdcxx_newness_check,
     onerror=die_on_old_libstdcxx,
@@ -1433,6 +1434,10 @@ set_config('_DEPEND_CFLAGS', depend_cfla
 set_config("_HOST_DEPEND_CFLAGS", depend_cflags(host_c_compiler))
 
 
+add_old_configure_assignment("CFLAGS", ["--gcc-toolchain=/usr/lib/gcc-mozilla"])
+add_old_configure_assignment("CXXFLAGS", ["--gcc-toolchain=/usr/lib/gcc-mozilla"])
+
+
 @depends(c_compiler)
 def preprocess_option(compiler):
     # The uses of PREPROCESS_OPTION depend on the spacing for -o/-Fi.
@@ -2137,6 +2142,7 @@ def linker_ldflags(linker, macos_sdk, ho
             flags.append("-Wl,--sysroot=%s" % macos_sdk)
     elif host.cpu == "arm":
         flags.append("-Wl,--no-keep-memory")
+    flags.append("-static-libstdc++")
     return flags
 
 
--- a/servo/components/style/build_gecko.rs
+++ b/servo/components/style/build_gecko.rs
@@ -149,6 +149,8 @@ impl BuilderExt for Builder {
             builder = builder.with_rustfmt(path);
         }
 
+        builder = builder.clang_arg("--gcc-toolchain=/usr/lib/gcc-mozilla");
+
         for dir in SEARCH_PATHS.iter() {
             builder = builder.clang_arg("-I").clang_arg(dir.to_str().unwrap());
         }
--- a/layout/style/test/moz.build
+++ b/layout/style/test/moz.build
@@ -18,6 +18,7 @@ DIRS += ['gtest']
         "host_ListCSSProperties",
     ]
 )
+HOST_CXXFLAGS += ["--gcc-toolchain=/usr/lib/gcc-mozilla"]
 
 MOCHITEST_MANIFESTS += [
     "mochitest.ini",