Bug 1540749 - Link Rust dead code and disable overflow checks to improve Rust coverage results. r=calixte

Differential Revision: https://phabricator.services.mozilla.com/D25624

--HG--
extra : moz-landing-system : lando

browser/config/mozconfigs/linux64/code-coverage

@@ -14,4 +14,4 @@ ac_add_options --enable-coverage
 
 export LDFLAGS="--coverage -L$topsrcdir/clang/lib/clang/7.0.1/lib/linux/"
 export LIBS="-lclang_rt.profile-x86_64"
-export RUSTFLAGS="-Ccodegen-units=1 -Zprofile -Zno-landing-pads"
+export RUSTFLAGS="-Ccodegen-units=1 -Zprofile -Zno-landing-pads -Clink-dead-code -Coverflow-checks=off"

browser/config/mozconfigs/macosx64/code-coverage

@@ -10,4 +10,4 @@ ac_add_options --enable-coverage
 
 export LDFLAGS="-coverage -L$topsrcdir/clang/lib/clang/7.0.1/lib/darwin/"
 export LIBS="-lclang_rt.profile_osx"
-export RUSTFLAGS="-Ccodegen-units=1 -Zprofile -Zno-landing-pads"
+export RUSTFLAGS="-Ccodegen-units=1 -Zprofile -Zno-landing-pads -Clink-dead-code -Coverflow-checks=off"

browser/config/mozconfigs/win64/code-coverage

@@ -28,7 +28,7 @@ if [ -d "$topsrcdir/clang" ]; then
     export LDFLAGS="clang_rt.profile-x86_64.lib"
 fi
 
-export RUSTFLAGS="-Ccodegen-units=1 -Zprofile -Zno-landing-pads"
+export RUSTFLAGS="-Ccodegen-units=1 -Zprofile -Zno-landing-pads -Clink-dead-code -Coverflow-checks=off"
 
 . "$topsrcdir/build/mozconfig.common.override"
 . "$topsrcdir/build/mozconfig.clang-cl"