Change dartpy install command to make install-dartpy

[jslee02]

Previously, DART provided two build modes, which is controlled by DART_BUILD_DARTPY: (1) build for the C++ package (as either shared or static libraries) or (2) build for the Python package (i.e. dartpy) enforcing to build the C++ libraries as static libraries. When installing the package, (1) installs the C++ headers and shared/static libraries while (b) only the binding module (i.e., dartpy.so). So we had to configure and build the package to build for both the C++ package and Python package.

However, there is a use case that requires to build dartpy against the shared libraries or/and build both the C++ and Python libraries without reconfiguring the package. This PR (i) removes the enforcement of static library build for dartpy and (ii) allows us to build dartpy without reconfiguring. For (ii), we still need to set DART_BUILD_DARTPY as ON though.

In short, here is the old behavior:

cmake .. -DDART_BUILD_DARTPY=OFF -DBUILD_SHARED_LIBS=ON   # to build as C++ package
make && make install                                      # build the shared libraries (`libdart.so`) and install them with the C++ headers

cmake .. -DDART_BUILD_DARTPY=OFF -DBUILD_SHARED_LIBS=OFF  # to build as C++ package
make && make install                                      # build the shared libraries (`libdart.a`) and install them with the C++ headers

rm -rf *                          # clean up the build directory

cmake .. -DDART_BUILD_DARTPY=ON   # to build as Python package
make dartpy                       # build the static libraries (`libdart.a`) and Python binding (`dartpy.so`)
                                  # BUILD_SHARED_LIBS is ignored
make install                      # install only `dartpy.so`

and the following is the new behavior:

cmake .. -DDART_BUILD_DARTPY=ON -DBUILD_SHARED_LIBS=ON
make && make install                # build the shared libraries (`libdart.so`) and install them with the C++ headers
make dartpy && make install-dartpy  # build the Python binding (`dartpy.so`) against the shared libraries (the shared library should be installed)

cmake .. -DDART_BUILD_DARTPY=ON -DBUILD_SHARED_LIBS=OFF
make && make install                # build the shared libraries (`libdart.so`) and install them with the C++ headers
make dartpy && make install-dartpy  # build the Python binding (`dartpy.so`) against the static libraries

cmake .. -DDART_BUILD_DARTPY=OFF
make && make install                # build the shared libraries (`libdart.so`) and install them with the C++ headers
make dartpy && make install-dartpy  # no such targets

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[codecov]

Codecov Report

Merging #1503 into master will not change coverage.
The diff coverage is n/a.

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  Misses      12552    12552