build: add support for building against conda TileDB and HTSLIB

For #47

apis/python/conda-env.yml

@@ -10,4 +10,4 @@ dependencies:
   - pip:
     - setuptools==39.0.1
     - pytest-runner==5.1
-    - pytest==5.1.2
+    - pytest==5.1.2

apis/python/setup.py

@@ -84,6 +84,21 @@ def find_libtiledbvcf():
     return None
 
 
+def get_cmake_env_config():
+    conf = list()
+
+    key = "TILEDBVCF_CMAKE_PREFIX_PATH"
+    val = os.environ.get(key, None)
+    if val:
+        conf.append("-DCMAKE_PREFIX_PATH={}".format(val))
+
+    key = "TILEDBVCF_FORCE_EXTERNAL_HTSLIB"
+    val = os.environ.get(key, None)
+    if val:
+        conf.append("-DTILEDBVCF_FORCE_EXTERNAL_HTSLIB={}".format(val))
+
+    return conf
+
 def build_libtiledbvcf():
     p = PathConfig()
 
@@ -98,6 +113,10 @@ def build_libtiledbvcf():
                  '-DFORCE_EXTERNAL_HTSLIB=ON',
                  '-DCMAKE_BUILD_TYPE=Release',
                  src_dir]
+
+    env_conf = get_cmake_env_config()
+    cmake_cmd.extend(env_conf)
+
     build_cmd = ['make', '-j{}'.format(multiprocessing.cpu_count() or 2)]
     install_cmd = ['make', 'install-libtiledbvcf']