Roll SPIRV-Tools from fcb22ecf0f7e to 615fbe6cbc78 (6 revisions)

https://chromium.googlesource.com/external/github.com/KhronosGroup/SPIRV-Tools.git/+log/fcb22ecf0f7e..615fbe6cbc78

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/spirv-tools-angle-autoroll
Please CC [email protected] on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/master/autoroll/README.md

Bug: None
Tbr: [email protected]
Change-Id: Ie48755f1b9097f2c54609c6d4ac3d81b4cee25bc
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2441348
Reviewed-by: angle-autoroll <[email protected]>
Commit-Queue: angle-autoroll <[email protected]>

Author: angle-autoroll

DEPS

@@ -80,7 +80,7 @@ vars = {
   'spirv_headers_revision': '3fdabd0da2932c276b25b9b4a988ba134eba1aa6',
 
   # Current revision of SPIRV-Tools for Vulkan.
-  'spirv_tools_revision': 'fcb22ecf0f7e7baa761c7ab01317cca5b14fcc35',
+  'spirv_tools_revision': '615fbe6cbc78463f6b58cecdb155dad0534d22b4',
 
   # Current revision of Khronos Vulkan-Headers.
   'vulkan_headers_revision': 'e1ba543c67893e13c7dae9bd38d3e5cba4ecb7c0',