MLBEDSW-6406: Restrict numpy version limit

 - The latest numpy versions require Python 3.8
 - This can cause issues if Python 3.7 is installed which is the version that
Vela is tested against
 - The fix is to limit the numpy version to those that support Python 3.7

Signed-off-by: Tim Hall <tim.hall@arm.com>
Change-Id: I3a388976d5aa76395ca93202e496640c8de9f6f4
diff --git a/setup.py b/setup.py
index d6e03b1..6036446 100644
--- a/setup.py
+++ b/setup.py
@@ -94,11 +94,11 @@
     python_requires="~=3.7",
     install_requires=[
         "flatbuffers==1.12.0",
-        "numpy",
+        "numpy<=1.21.6",
         "lxml>=4.5.1",
     ],
     entry_points={"console_scripts": ["vela = ethosu.vela.vela:main"]},
     ext_modules=[mlw_module],
     cmdclass={"build_ext": BuildExtension},  # type: ignore[dict-item]
-    setup_requires=["numpy", "setuptools_scm"],
+    setup_requires=["numpy<=1.21.6", "setuptools_scm"],
 )