Auto merge of #19353 - servo:jdm-patch-7, r=KiChjang

Add clang packages for non-debian linuxes.

Per servo/gecko-media#71 (comment).

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README.md

@@ -75,7 +75,7 @@ sudo dnf install curl freeglut-devel libtool gcc-c++ libXi-devel \
     freetype-devel mesa-libGL-devel mesa-libEGL-devel glib2-devel libX11-devel libXrandr-devel gperf \
     fontconfig-devel cabextract ttmkfdir python python-virtualenv python-pip expat-devel \
     rpm-build openssl-devel cmake bzip2-devel libXcursor-devel libXmu-devel mesa-libOSMesa-devel \
-    dbus-devel ncurses-devel pulseaudio-libs-devel
+    dbus-devel ncurses-devel pulseaudio-libs-devel clang clang-libs
 ```
 #### On CentOS
 
@@ -84,15 +84,15 @@ sudo yum install curl freeglut-devel libtool gcc-c++ libXi-devel \
     freetype-devel mesa-libGL-devel mesa-libEGL-devel glib2-devel libX11-devel libXrandr-devel gperf \
     fontconfig-devel cabextract ttmkfdir python python-virtualenv python-pip expat-devel \
     rpm-build openssl-devel cmake bzip2-devel libXcursor-devel libXmu-devel mesa-libOSMesa-devel \
-    dbus-devel ncurses-devel python34 pulseaudio-libs-devel
+    dbus-devel ncurses-devel python34 pulseaudio-libs-devel clang clang-libs
 ```
 
 #### On openSUSE Linux
 ``` sh
 sudo zypper install libX11-devel libexpat-devel libbz2-devel Mesa-libEGL-devel Mesa-libGL-devel cabextract cmake \
     dbus-1-devel fontconfig-devel freetype-devel gcc-c++ git glib2-devel gperf \
     harfbuzz-devel libOSMesa-devel libXcursor-devel libXi-devel libXmu-devel libXrandr-devel libopenssl-devel \
-    python-pip python-virtualenv rpm-build glu-devel
+    python-pip python-virtualenv rpm-build glu-devel llvm-clang libclang
 ```
 #### On Arch Linux