vijaypradeep@vijaypradeep-vm:~/scratch/cmake_bug$ lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 14.04.1 LTS
Release:	14.04
Codename:	trusty
vijaypradeep@vijaypradeep-vm:~/scratch/cmake_bug$ cmake --version
cmake version 2.8.12.2
vijaypradeep@vijaypradeep-vm:~/scratch/cmake_bug$ ls
CMakeLists.txt
vijaypradeep@vijaypradeep-vm:~/scratch/cmake_bug$ cat CMakeLists.txt 
cmake_minimum_required(VERSION 2.8)

add_library(mybaz baz.cpp)

add_custom_command(
  OUTPUT baz2.cpp
  COMMAND cp baz.cpp baz2.cpp
  DEPENDS baz.cpp
  COMMENT "Copying baz.cpp to baz2.cpp")

add_custom_target(mytarget
  DEPENDS baz2.cpp
  COMMENT "Running mytarget")

add_dependencies(mybaz mytarget)

add_custom_command(
  OUTPUT bar.cpp baz.cpp
  COMMAND cat a.txt > bar.cpp
  COMMAND cat a.txt > baz.cpp
  DEPENDS a.txt
  COMMENT "Generating bar.cpp and baz.cpp")
vijaypradeep@vijaypradeep-vm:~/scratch/cmake_bug$ touch a.txt
vijaypradeep@vijaypradeep-vm:~/scratch/cmake_bug$ cmake .
-- The C compiler identification is GNU 4.8.2
-- The CXX compiler identification is GNU 4.8.2
-- Check for working C compiler: /usr/lib/ccache/cc
-- Check for working C compiler: /usr/lib/ccache/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working CXX compiler: /usr/lib/ccache/c++
-- Check for working CXX compiler: /usr/lib/ccache/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Configuring done
-- Generating done
-- Build files have been written to: /home/vijaypradeep/scratch/cmake_bug
vijaypradeep@vijaypradeep-vm:~/scratch/cmake_bug$ make
Scanning dependencies of target mytarget
[ 20%] Generating bar.cpp and baz.cpp
[ 40%] Copying baz.cpp to baz2.cpp
[ 60%] Running mytarget
[ 60%] Built target mytarget
Scanning dependencies of target mybaz
[ 80%] Building CXX object CMakeFiles/mybaz.dir/baz.cpp.o
Linking CXX static library libmybaz.a
[100%] Built target mybaz
vijaypradeep@vijaypradeep-vm:~/scratch/cmake_bug$ touch a.txt
vijaypradeep@vijaypradeep-vm:~/scratch/cmake_bug$ make
[ 20%] Generating bar.cpp and baz.cpp
[ 40%] Running mytarget
[ 60%] Built target mytarget
Scanning dependencies of target mybaz
[ 80%] Building CXX object CMakeFiles/mybaz.dir/baz.cpp.o
Linking CXX static library libmybaz.a
[100%] Built target mybaz
vijaypradeep@vijaypradeep-vm:~/scratch/cmake_bug$ make
[ 20%] Copying baz.cpp to baz2.cpp
[ 40%] Running mytarget
[ 60%] Built target mytarget
[100%] Built target mybaz
vijaypradeep@vijaypradeep-vm:~/scratch/cmake_bug$