provide an alternate way to set liboqs path (#95)

Also check lib64 directory for liboqs

Signed-off-by: Vysakh P Pillai <vysakhpillai@gmail.com>
Signed-off-by: Vysakh Pillai <vysakhpillai@gmail.com>

Author: vppillai

README.md

@@ -84,6 +84,12 @@ an alternative path, e.g., `C:\liboqs`, by passing the
 cmake -S liboqs -B liboqs/build -DCMAKE_INSTALL_PREFIX="C:\liboqs" -DCMAKE_WINDOWS_EXPORT_ALL_SYMBOLS=TRUE -DBUILD_SHARED_LIBS=ON
 ```
 
+Alternatively you can set the `OQS_INSTALL_PATH` environment variable to point to the installation directory, e.g., on a UNIX-like system execute:
+
+```shell
+export OQS_INSTALL_PATH=/path/to/liboqs
+```
+
 ### Let liboqs-python install liboqs automatically
 
 If liboqs is not detected at runtime by liboqs-python, it will be downloaded,

oqs/oqs.py

@@ -108,15 +108,24 @@ def _install_liboqs(target_directory, oqs_version=None):
 
 
 def _load_liboqs():
-    home_dir = os.path.expanduser("~")
-    oqs_install_dir = os.path.abspath(home_dir + os.path.sep + "_oqs")  # $HOME/_oqs
+    if "OQS_INSTALL_PATH" in os.environ:
+        oqs_install_dir = os.path.abspath(os.environ["OQS_INSTALL_PATH"])
+    else:    
+        home_dir = os.path.expanduser("~")
+        oqs_install_dir = os.path.abspath(home_dir + os.path.sep + "_oqs")  # $HOME/_oqs
+        
     oqs_lib_dir = (
         os.path.abspath(oqs_install_dir + os.path.sep + "bin")  # $HOME/_oqs/bin
         if platform.system() == "Windows"
         else os.path.abspath(oqs_install_dir + os.path.sep + "lib")  # $HOME/_oqs/lib
     )
+    oqs_lib64_dir = (
+        os.path.abspath(oqs_install_dir + os.path.sep + "bin")  # $HOME/_oqs/bin
+        if platform.system() == "Windows"
+        else os.path.abspath(oqs_install_dir + os.path.sep + "lib64")  # $HOME/_oqs/lib64
+    )
     try:
-        _liboqs = _load_shared_obj(name="oqs", additional_searching_paths=[oqs_lib_dir])
+        _liboqs = _load_shared_obj(name="oqs", additional_searching_paths=[oqs_lib_dir, oqs_lib64_dir])
         assert _liboqs
     except RuntimeError:
         # We don't have liboqs, so we try to install it automatically