Add pyproject.toml for build dependencies

Following PEP 518 so that scikit-build can be automatically downloaded
when trying to build from an sdist.

Author: blowekamp

pyproject.toml

@@ -0,0 +1,2 @@
+[build-system]
+requires = ["scikit-build >= 0.11", "wheel", "cmake", "ninja"]

requirements-dev.txt

@@ -1 +1 @@
-scikit-build==0.5.0
+scikit-build>=0.11

setup.py

@@ -1,13 +1,6 @@
 from __future__ import print_function
 from os import sys
-try:
-    from skbuild import setup
-except ImportError:
-    print('scikit-build is required to build from source.', file=sys.stderr)
-    print('Please run:', file=sys.stderr)
-    print('', file=sys.stderr)
-    print('  python -m pip install scikit-build')
-    sys.exit(1)
+from skbuild import setup
 
 
 setup(