Steps to reproduce:
1. Open the attached project(ShaderTest.zip)
2. Open Build Settings
3. Go to Player Settings -> Other Settings and uncheck Auto Graphics API for Windows
4. Add OpenGL and put it at the top of the list
5. Select the Debug shader in the Project window
6. Observe the error:
GLSL link error: Geometry info
0(3) : warning C7508: extension ARB_geometry_shader not supported
error: interpolation modifier mismatch for varying parameter (named vs_INDICES0) between shader stages

Expected result: Shader should compile
Actual result: Unity throws the error

Note:
Reproduced with GeForce GTX 750 TI
Does not reproduce on AMD R7 360. Shader does not turn pink. Only thrown an error is:
The given primitive topology does not match with the topology expected by the geometry shader

Reproduced with: 5.4.5p3, 5.5.4f1, 5.6.1p3, 2017.1.0b9, 2017.2.0a3