Install cp315 numpy from the nightly index instead of building from source

PyPI publishes no cp315/cp315t numpy wheels, so `pip install numpy` in the
smoke-test step falls back to a source build. That is merely slow on Linux and
macOS, but a hard failure on Windows:

    numpy/_core/src/common/simd/simd.h(4): fatal error C1083:
        Cannot open include file: 'stdalign.h': No such file or directory
    error: metadata-generation-failed

download.pytorch.org/whl/nightly carries preview cp315 and cp315t numpy wheels
for every platform (manylinux x86_64/aarch64, macosx arm64/x86_64, win_amd64),
so pull numpy from there for 3.15 and forbid a source fallback with
--only-binary=:all:. Other python versions keep using PyPI unchanged.

Author: atalman

.github/scripts/validate_binaries.sh

@@ -200,7 +200,19 @@ run_smoke_tests() {
 
     # For pip install also test with latest numpy
     if [[ ${MATRIX_PACKAGE_TYPE} == 'wheel' ]]; then
-        pip3 install numpy --upgrade --force-reinstall
+        # PyPI publishes no cp315/cp315t numpy wheels, so a plain
+        # `pip install numpy` falls back to building from source: slow on Linux
+        # and macOS, and a hard failure on Windows, where MSVC cannot find
+        # stdalign.h ("fatal error C1083") while compiling numpy's SIMD headers.
+        # Preview wheels for every platform, Windows included, are on the
+        # nightly index -- take those instead, and never a source build.
+        if [[ ${MATRIX_PYTHON_VERSION} == "3.15" || ${MATRIX_PYTHON_VERSION} == "3.15t" ]]; then
+            pip3 install --pre numpy --upgrade --force-reinstall \
+                --only-binary=:all: \
+                --index-url https://download.pytorch.org/whl/nightly
+        else
+            pip3 install numpy --upgrade --force-reinstall
+        fi
         ${PYTHON_RUN} ./smoke_test/smoke_test.py ${test_suffix} ${compile_check}
     fi