remove the compiler-rt submodule

Author: Jorge Aparicio

.gitmodules

@@ -2,9 +2,6 @@
 	path = src/llvm
 	url = https://github.com/rust-lang/llvm.git
 	branch = master
-[submodule "src/compiler-rt"]
-	path = src/compiler-rt
-	url = https://github.com/rust-lang/compiler-rt.git
 [submodule "src/rt/hoedown"]
 	path = src/rt/hoedown
 	url = https://github.com/rust-lang/hoedown.git