Fix build error on Cygwin due to inappropriate linker flag

Author: molinav

CHANGELOG.md

@@ -19,8 +19,10 @@ https://semver.org/spec/v2.0.0.html
 - Upgrade documentation and linting dependencies.
 
 ### Fixed
+- Fix Cygwin build error due to GCC passing `"--enable-new-dtags"` to
+  the linker (solves issue [#579], thanks to @DWesl for the help).
 - Fix deprecated `Image.ANTIALIAS` with `Image.LANCZOS` when `pillow`
-  version is at least 10.0.0 (PR [#580], thanks to @cgohlke).
+  version is at least 10.0.0 (PR [#580] by @cgohlke).
 - Downgrade upper pin for Cython requirement from 3.1 to 3.0 due to
   build error triggered by `_geoslib.pyx` (solves issue [#581]).
 - Downgrade lower pin for `numpy` to `>= 1.21` for Python >= 3.8, whose
@@ -977,6 +979,8 @@ https://semver.org/spec/v2.0.0.html
 https://github.com/matplotlib/basemap/issues/581
 [#580]:
 https://github.com/matplotlib/basemap/pull/580
+[#579]:
+https://github.com/matplotlib/basemap/issues/579
 [#573]:
 https://github.com/matplotlib/basemap/issues/573
 [#564]:

packages/basemap/setup.py

@@ -111,7 +111,7 @@ def run(self):
     library_dirs.append(os.path.join(geos_install_prefix, "lib"))
     library_dirs.append(os.path.join(geos_install_prefix, "lib64"))
     runtime_library_dirs = library_dirs
-    if os.name == "nt":
+    if os.name == "nt" or sys.platform == "cygwin":
         # On Windows:
         # - DLLs get installed under `bin`.
         # - We need to inject later the DLL in the wheel using `data_files`.