Fix python's lib folder search on virtualenv

the current way to find it looks for a file that was changed after a
refactor `virtualenv` had

gvsbuild/utils/utils.py

@@ -120,20 +120,37 @@ def python_find_libs_dir(org_dir):
         # easy :)
         return cur
 
+    org_found = False
     # look for the virtualenv marker
-    chk = os.path.join(org_dir, "lib")
-    if not os.path.isdir(chk):
+    pyvenv_file = os.path.join(org_dir, "pyvenv.cfg")
+    if not os.path.isfile(pyvenv_file):
         # one level up
-        chk = os.path.join(org_dir, "..", "lib")
-
-    if not chk:
-        # oops
-        return None
+        pyvenv_file = os.path.join(org_dir, "..", "pyvenv.cfg")
+
+    if os.path.isfile(pyvenv_file):
+        # Read file to get home path
+        for line in read_file(pyvenv_file):
+            key, value = line.split("=")
+            if "home" == key.strip():
+                org_dir = value.strip()
+                org_found = True
+                break
 
-    orig_file = os.path.join(chk, "orig-prefix.txt")
-    if os.path.isfile(orig_file):
-        # Read and see what's happening
-        org_dir = pathlib.Path(orig_file).read_text()
+    if not org_found:
+        # look for the virtualenv marker (legacy)
+        chk = os.path.join(org_dir, "lib")
+        if not os.path.isdir(chk):
+            # one level up
+            chk = os.path.join(org_dir, "..", "lib")
+
+        if not chk:
+            # oops
+            return None
+
+        orig_file = os.path.join(chk, "orig-prefix.txt")
+        if os.path.isfile(orig_file):
+            # Read and see what's happening
+            org_dir = pathlib.Path(orig_file).read_text()
     # Let's see if now is ok ..
     cur = os.path.join(org_dir, "libs")
     return cur if os.path.isdir(cur) else None