gh-116472: Replace literal newlines with escape characters in MSBuild files (GH-116473)

(cherry picked from commit 5d0cdfe)

Co-authored-by: Dan Albert <dan@gingerhq.net>

Author: miss-islington

PCbuild/regen.targets

@@ -109,9 +109,7 @@
           Condition="($(Platform) == 'Win32' or $(Platform) == 'x64') and
                      $(Configuration) != 'PGInstrument' and $(Configuration) != 'PGUpdate'">
     <Message Text="Regenerate @(_TestFrozenOutputs->'%(Filename)%(Extension)', ' ')" Importance="high" />
-    <Exec Command='setlocal
-set PYTHONPATH=$(PySourcePath)Lib
-"$(PythonExe)" Programs\freeze_test_frozenmain.py Programs\test_frozenmain.h'
+    <Exec Command='setlocal%0D%0Aset PYTHONPATH=$(PySourcePath)Lib%0D%0A"$(PythonExe)" Programs\freeze_test_frozenmain.py Programs\test_frozenmain.h'
           WorkingDirectory="$(PySourcePath)" />
   </Target>