impellerc flaky failing build on Windows in engine CI #105709
Description
An example is here https://ci.chromium.org/ui/p/flutter/builders/prod/Windows%20Unopt/5930/overview
FAILED: gen/flutter/impeller/entity/genlib_gles_entity_shaders.shaderblob
C:/b/s/w/ir/cipd_bin_packages/cpython3/bin/python3.exe ../../build/gn_run_binary.py blobcat.exe --output=gen/flutter/impeller/entity/genlib_gles_entity_shaders.shaderblob --input=gen/flutter/impeller/entity/advanced_blend.vert.gles --input=gen/flutter/impeller/entity/advanced_blend_color.frag.gles --input=gen/flutter/impeller/entity/advanced_blend_colorburn.frag.gles --input=gen/flutter/impeller/entity/advanced_blend_colordodge.frag.gles --input=gen/flutter/impeller/entity/advanced_blend_darken.frag.gles --input=gen/flutter/impeller/entity/advanced_blend_difference.frag.gles --input=gen/flutter/impeller/entity/advanced_blend_exclusion.frag.gles --input=gen/flutter/impeller/entity/advanced_blend_hardlight.frag.gles --input=gen/flutter/impeller/entity/advanced_blend_hue.frag.gles --input=gen/flutter/impeller/entity/advanced_blend_lighten.frag.gles --input=gen/flutter/impeller/entity/advanced_blend_luminosity.frag.gles --input=gen/flutter/impeller/entity/advanced_blend_multiply.frag.gles --input=gen/flutter/impeller/entity/advanced_blend_overlay.frag.gles --input=gen/flutter/impeller/entity/advanced_blend_saturation.frag.gles --input=gen/flutter/impeller/entity/advanced_blend_screen.frag.gles --input=gen/flutter/impeller/entity/advanced_blend_softlight.frag.gles --input=gen/flutter/impeller/entity/blend.frag.gles --input=gen/flutter/impeller/entity/blend.vert.gles --input=gen/flutter/impeller/entity/border_mask_blur.frag.gles --input=gen/flutter/impeller/entity/border_mask_blur.vert.gles --input=gen/flutter/impeller/entity/gaussian_blur.frag.gles --input=gen/flutter/impeller/entity/gaussian_blur.vert.gles --input=gen/flutter/impeller/entity/glyph_atlas.frag.gles --input=gen/flutter/impeller/entity/glyph_atlas.vert.gles --input=gen/flutter/impeller/entity/gradient_fill.frag.gles --input=gen/flutter/impeller/entity/gradient_fill.vert.gles --input=gen/flutter/impeller/entity/solid_fill.frag.gles --input=gen/flutter/impeller/entity/solid_fill.vert.gles --input=gen/flutter/impeller/entity/solid_stroke.frag.gles --input=gen/flutter/impeller/entity/solid_stroke.vert.gles --input=gen/flutter/impeller/entity/texture_fill.frag.gles --input=gen/flutter/impeller/entity/texture_fill.vert.gles --input=gen/flutter/impeller/entity/vertices.vert.gles --input=gen/flutter/impeller/entity/vertices.frag.gles
[ERROR:flutter/fml/platform/win/file_win.cc(365)] Could not create temporary file.
Could not write shader blob to path gen/flutter/impeller/entity/genlib_gles_entity_shaders.shaderblob
Not sure where this started happening. First instance was on a Skia roll, but the commit right before was flutter/engine#33824, which was the change to use impellerc for FragmentProgram API unit tests, so guessing it might be related.