add_executable
--------------

Add an executable to the project using the specified source files.

::

  add_executable(<name> [WIN32] [MACOSX_BUNDLE]
                 [EXCLUDE_FROM_ALL]
                 source1 source2 ... sourceN)

Adds an executable target called <name> to be built from the source
files listed in the command invocation.  The <name> corresponds to the
logical target name and must be globally unique within a project.  The
actual file name of the executable built is constructed based on
conventions of the native platform (such as <name>.exe or just
<name>).

By default the executable file will be created in the build tree
directory corresponding to the source tree directory in which the
command was invoked.  See documentation of the
RUNTIME_OUTPUT_DIRECTORY target property to change this location.  See
documentation of the OUTPUT_NAME target property to change the <name>
part of the final file name.

If WIN32 is given the property WIN32_EXECUTABLE will be set on the
target created.  See documentation of that target property for
details.

If MACOSX_BUNDLE is given the corresponding property will be set on
the created target.  See documentation of the MACOSX_BUNDLE target
property for details.

If EXCLUDE_FROM_ALL is given the corresponding property will be set on
the created target.  See documentation of the EXCLUDE_FROM_ALL target
property for details.

The add_executable command can also create IMPORTED executable targets
using this signature:

::

  add_executable(<name> IMPORTED [GLOBAL])

An IMPORTED executable target references an executable file located
outside the project.  No rules are generated to build it.  The target
name has scope in the directory in which it is created and below, but
the GLOBAL option extends visibility.  It may be referenced like any
target built within the project.  IMPORTED executables are useful for
convenient reference from commands like add_custom_command.  Details
about the imported executable are specified by setting properties
whose names begin in "IMPORTED_".  The most important such property is
IMPORTED_LOCATION (and its per-configuration version
IMPORTED_LOCATION_<CONFIG>) which specifies the location of the main
executable file on disk.  See documentation of the IMPORTED_*
properties for more information.

The signature

::

  add_executable(<name> ALIAS <target>)

creates an alias, such that <name> can be used to refer to <target> in
subsequent commands.  The <name> does not appear in the generated
buildsystem as a make target.  The <target> may not be an IMPORTED
target or an ALIAS.  Alias targets can be used as linkable targets,
targets to read properties from, executables for custom commands and
custom targets.  They can also be tested for existance with the
regular if(TARGET) subcommand.  The <name> may not be used to modify
properties of <target>, that is, it may not be used as the operand of
set_property, set_target_properties, target_link_libraries etc.  An
ALIAS target may not be installed of exported.
