[Regression] Shader no longer compiles on selected APIs, gives cryptic errors.

Hello,

I just uploaded a bug report with a shader that no longer compiles at least on GLES3 and OpenGLCore.

When attempting to compile it for these APIs, I get the following error :
Shader compiler: internal error compiling shader snippet type=[0|1] platform=<API_ID>: Protocol error - failed to read correct magic number

My other shaders have no issue, so I guess it has something to do with the specific depth stuff done in it.
The case number is 830427 and the shaders code is the following :

Spoiler: Shader code

Code (CSharp):

1. Shader "Hidden/PKFx Depth Copy"
2. {
3.     Properties
4.     {
5.         _Flip("Set to 1 when in forward rendering.", Range(0, 1)) = 0.0
6.     }
7.     SubShader
8.     {
9.         // No culling or depth
10.         ZTest Always
11.         ZWrite On
12.  
13.         // Writes to a single-component texture (TextureFormat.Depth)
14.         Pass
15.         {
16.             CGPROGRAM
17.             #pragma vertex vert
18.             #pragma fragment frag
19.  
20.             #include "UnityCG.cginc"
21.  
22.             struct appdata
23.             {
24.                 float4 vertex : POSITION;
25.                 float2 uv : TEXCOORD0;
26.             };
27.  
28.             struct v2f
29.             {
30.                 fixed2 uv : TEXCOORD0;
31.                 float4 vertex : SV_POSITION;
32.             };
33.  
34.             float _Flip;
35.  
36.             v2f vert(appdata v)
37.             {
38.                 v2f o;
39.                 o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);
40.                 o.uv = v.uv * (1 - _Flip) + _Flip * float2(v.uv.x, 1 - v.uv.y);
41.                 return o;
42.             }
43.  
44.             sampler2D _CameraDepthTexture;
45.  
46. #if !defined(SHADER_API_D3D9) && !defined(SHADER_API_D3D11_9X)
47.             fixed frag(v2f i) : SV_Depth
48.             {
49.                 fixed4 col = tex2D(_CameraDepthTexture, i.uv);
50.                 return col.r;
51.             }
52. #else
53.             void frag(v2f i, out float4 dummycol:COLOR, out float depth : DEPTH)
54.             {
55.                 fixed4 col = tex2D(_CameraDepthTexture, i.uv);
56.                 dummycol = col;
57.  
58.                 depth = col.r;
59.             }
60. #endif
61.             ENDCG
62.         }
63.     }
64. }
65.