diff -Naur PyQt-builder-1.4.0-orig/pyqtbuild/builder.py PyQt-builder-1.4.0/pyqtbuild/builder.py
--- PyQt-builder-1.4.0-orig/pyqtbuild/builder.py	2020-05-31 14:52:54.000000000 +0300
+++ PyQt-builder-1.4.0/pyqtbuild/builder.py	2020-06-07 21:33:19.550266500 +0300
@@ -26,6 +26,7 @@
 
 import os
 import sys
+from sysconfig import _POSIX_BUILD
 
 from sipbuild import (Buildable, BuildableModule, Builder, Option, Project,
         PyProjectOptionException, UserException)
@@ -58,7 +59,7 @@
             # be on PATH).
             if tool != 'pep517':
                 self._sip_distinfo = os.path.join(
-                        os.path.abspath(os.path.dirname(sys.argv[0])),
+                        os.path.abspath(os.path.dirname(sys.argv[0]).replace('\\', '/')),
                         self._sip_distinfo)
 
             # Check we have a qmake.
@@ -175,8 +175,12 @@
                             ['install_' + installable.name
                                     for installable in project.installables])))
             pro_lines.append('distinfo.extra = {}'.format(' '.join(args)))
+            if self.project.py_platform == 'win32' and "MSYSTEM" in os.environ:
+                distinfo_dir = os.popen(' '.join(['cygpath', '--unix', target_dir])).readline().strip()
+            else:
+                distinfo_dir = target_dir
             pro_lines.append(
-                    'distinfo.path = {}'.format(self.qmake_quote(target_dir)))
+                    'distinfo.path = {}'.format(self.qmake_quote(distinfo_dir)))
             pro_lines.append('INSTALLS += distinfo')
 
         pro_name = os.path.join(project.build_dir, project.name + '.pro')
@@ -266,7 +267,7 @@
     def _find_make(self):
         """ Return the name of a valid make program. """
 
-        if self.project.py_platform == 'win32':
+        if self.project.py_platform == 'win32' and not "MSYSTEM" in os.environ:
             if self.spec == 'win32-g++':
                 make = 'mingw32-make'
             else:
@@ -388,8 +389,8 @@
         # TODO: is this still necessary for Python v3.8?
         if not buildable.static:
             pro_lines.extend(['win32 {',
-                    '    LIBS += -L{}'.format(
-                            self.qmake_quote(project.py_pylib_dir)),
+                    '    LIBS += -L{} -l{}'.format(
+                            self.qmake_quote(project.py_pylib_dir), self.qmake_quote(project.py_pylib_lib)),
                     '}'])
 
         # Add any installables from the buildable.
@@ -419,7 +420,11 @@
                     raise UserException(
                             "Unexpected output from qmake: '{0}'".format(line))
 
-                name, value = tokens
+                if _POSIX_BUILD and "MSYSTEM" in os.environ:
+                    name = tokens[0]
+                    value = os.popen(' '.join(['cygpath', '--unix', tokens[1]])).readline().strip()
+                else:
+                    name, value = tokens
             else:
                 name = tokens
                 value = None
diff -Naur PyQt-builder-1.4.0-orig/pyqtbuild/project.py PyQt-builder-1.4.0/pyqtbuild/project.py
--- PyQt-builder-1.4.0-orig/pyqtbuild/project.py	2020-05-31 14:52:54.000000000 +0300
+++ PyQt-builder-1.4.0/pyqtbuild/project.py	2020-06-07 21:31:10.233125300 +0300
@@ -26,6 +26,7 @@
 
 import os
 import sys
+from sysconfig import _POSIX_BUILD
 
 from sipbuild import Option, Project
 
@@ -88,7 +89,7 @@
         # Get the details of the default Python interpreter library.  Note that
         # these are actually non-user options but we need the 'link_full_dll'
         # user option in order to set them.
-        if self.py_platform == 'win32':
+        if self.py_platform == 'win32' and not _POSIX_BUILD:
             pylib_dir = os.path.join(sys.base_prefix, 'libs')
 
             debug_suffix = '_d' if self.py_debug else ''