CDB & GDB exit with 0xC0000017 when attempting to debug a TEMPLATE = subdirs project

Debugging a subdirs project with a number of small subprojects may cause CDB & GDB to instantly exit with 0xC0000017.

The problem seems to be related to the length of the build directory path. For build directories with a long path the problem occurs with both debuggers and for build directories with considerably shorter path the problem does not occur.

Debugging the project from command line works without problems either way. The project runs otherwise fine too.

When the problem occurred CDB log didn't seem to contain anything strange. GDB log on the other hand contained:

Setting breakpoints...

18-gdb-set environment PATH=

Followed by a value where the path to the subdirs was repeated a few hundred times. Check the attached gdb.log for reference.

Steps to reproduce:

1. Set build directory path to be long (e.g. C:\test_dir\veeeeeeeeeeeery\looooooooooooong\paaaaaaaaaaaaaath <- actually tested with this)
2. Attempt to debug the project (=> expecting debugger to exit with 0xC0000017)
3. Shorten the build directory path (e.g. C:\test_dir\b)
4. Attempt to debug the project (=> debugging works)