cmake: directory --> folder; fix typo

pages/common/cmake.md

@@ -3,13 +3,13 @@
 > Cross-platform build system generator.
 > It generates Makefiles, Visual Studio projects or others, depending on the target system.
 
-- Generate a Makefile and use it to compile a project in the same directory as the source:
+- Generate a Makefile and use it to compile a project in the same folder as the source:
 
 `cmake && make`
 
-- Generate a Makefule and use it to compile a project in a separate directory (out-of-source build):
+- Generate a Makefile and use it to compile a project in a separate folder (out-of-source build):
 
-`cd {{build_dir}} && cmake ../ && make`
+`cd {{build_folder}} && cmake ../ && make`
 
 - Run cmake in interactive mode (it will ask for each variable, instead of using defaults):