Fix cmake target compilation command example
Fix typo DCMAKE_C_COMPILERC -> DCMAKE_C_COMPILER.
Add `cd build` after `mkdir build`.
MODIFY
README.md
README.md
@@ -436,7 +436,7 @@ described in [instrumentation/README.lto.md](instrumentation/README.lto.md).
##### cmake
For `cmake` build systems this is usually done by:
-`mkdir build; cmake -DCMAKE_C_COMPILERC=afl-cc -DCMAKE_CXX_COMPILER=afl-c++ ..`
+`mkdir build; cd build; cmake -DCMAKE_C_COMPILER=afl-cc -DCMAKE_CXX_COMPILER=afl-c++ ..`
Note that if you are using the (better) afl-clang-lto compiler you also have to
set AR to llvm-ar[-VERSION] and RANLIB to llvm-ranlib[-VERSION] - as is

Fix cmake target compilation command example (#934)

- Fix typo DCMAKE_C_COMPILERC -> DCMAKE_C_COMPILER.
- Add `cd build` after `mkdir build`.