uniforms of type bool are transpiled as uint when targeting #version 100

[elizagamedev]

As the title says. This results in an exception

Unsigned integers are not supported on legacy ESSL.

To reproduce:

#version 310 es

layout(binding = 0) uniform Foo {
  bool bar;
} foo;

void main() {}

Disabling the relevant checks in spirv_glsl.cpp showed that bar was indeed changed into a uint.