Fix generated -DNOTFOUND for compiling elementwise functions

[oleksandr-pavlyk]

E.g.

[123/222] $BUILD_PREFIX/bin/icpx -D_tensor_elementwise_impl_EXPORTS -DNOTFOUND -DUSE_SYCL_FOR_COMPLEX_TYPES \
     -I$BUILD_PREFIX/include \
     .... \
     -c $SRC_DIR/dpctl/tensor/libtensor/source/elementwise_functions/acos.cpp

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[github-actions]

Deleted rendered PR docs from intelpython.github.com/dpctl, latest should be updated shortly. 🤞

[coveralls]

coverage: 91.0%. remained the same
when pulling 5e539f9 on fix-DNOTFOUND-in-cmake-script
into 9b0a3cd on master.

[github-actions]

Array API standard conformance tests for dpctl=0.15.1dev3=py310h15de555_40 ran successfully.
Passed: 909
Failed: 0
Skipped: 86

[oleksandr-pavlyk]

From logs, the -DNOTFOUND is gone:

[152/222] $BUILD_PREFIX/bin/icpx -D_tensor_elementwise_impl_EXPORTS -DUSE_SYCL_FOR_COMPLEX_TYPES \
     -I$BUILD_PREFIX/include \
      .... \
      -c $SRC_DIR/dpctl/tensor/libtensor/source/elementwise_functions/floor_divide.cpp