Get rid of build configuration from l10n mozconfigs (followup to bug 1426555); r=me

--HG--
extra : rebase_source : c27ab9bc4a17cc0d5e8ef123d7ba3d8f0b3fb3bf
extra : amend_source : c8b796df278333000c8d94d4a850f946ae8c3530
extra : source : 0748052c1285131deb74f5e06a178a3a7c650d95

mail/config/mozconfigs/linux32/l10n-mozconfig

@@ -1,4 +1,3 @@
 . "$topsrcdir/build/mozconfig.comm-support"
 . "$commtopsrcdir/mail/config/mozconfigs/l10n-common"
 
-ac_add_options --disable-stdcxx-compat

mail/config/mozconfigs/linux64/l10n-mozconfig

@@ -1,4 +1,2 @@
 . "$topsrcdir/build/mozconfig.comm-support"
 . "$commtopsrcdir/mail/config/mozconfigs/l10n-common"
-
-ac_add_options --disable-stdcxx-compat

mail/config/mozconfigs/win64/l10n-mozconfig

@@ -1,8 +1,5 @@
 . "$topsrcdir/build/mozconfig.comm-support"
 . "$commtopsrcdir/mail/config/mozconfigs/l10n-common"
 
-ac_add_options --target=x86_64-pc-mingw32
-ac_add_options --host=x86_64-pc-mingw32
-
 # Use the TOOLTOOL provided xz for mar generation.
 mk_add_options "export XZ=$TOOLTOOL_DIR/xz/xz.exe"