building: avoid importing PySimpleGUI prior to binary dep. analysis

Add `PySimpleGUI` to the list of packages whose import should be
explicitly suppressed when importing packages for tracking of
dynamic library search path modifications prior to binary
dependency analysis.

`PySimpleGUI` 5.x displays a "first-run" dialog when imported
for the first time, which breaks unattended PyInstaller builds
(for example, building on CI, where the dialog cannot be closed
but will be shown every time due to clean environment).

PyInstaller/building/build_main.py

@@ -246,6 +246,11 @@ def process_search_paths():
         # well as https://github.com/pyqtgraph/pyqtgraph/issues/2838.
         suppressed_imports += ['pyqtgraph.canvas']
 
+        # PySimpleGUI 5.x displays a "first-run" dialog when imported for the first time, which blocks the loop below.
+        # This is a problem for building on CI, where the dialog cannot be closed, and where PySimpleGUI runs "for the
+        # first time" every time. See #8396.
+        suppressed_imports += ['PySimpleGUI']
+
         # Processing in isolated environment.
         with isolated.Python() as child:
             child.call(setup, suppressed_imports)

news/8396.bugfix.rst

@@ -0,0 +1,6 @@
+(Windows) Avoid trying to import ``PySimpleGUI`` in the subprocess that
+analyzes dynamic library search modifications made by packages prior to
+the binary dependency analysis. When imported for the first time,
+``PySimpleGUI`` 5.x displays a "first-run" dialog, which poses a problem
+for unattended PyInstaller builds running in a clean environment, for
+example, in a CI pipeline.