I've also run into this issue, although a workaround exists (see:
https://github.com/magnumripper/JohnTheRipper/issues/2204).  The problem
appears to be with the declaration of 'inline'; removing the 'inline'
declaration fixes the compilation issue.

Hardware/software information as follows is:
frostsnow@seneca ~/software/JohnTheRipper/run $ ./john --list=OpenCL-devices
Platform #0 name: Clover, version: OpenCL 1.1 Mesa 12.0.1
    Device #0 (0) name:     AMD HAWAII (DRM 2.45.0 / 4.7.0, LLVM 3.8.1)
    Device vendor:          AMD
    Device type:            GPU (LE)
    Device version:         OpenCL 1.1 Mesa 12.0.1
    Driver version:         12.0.1 - Catalyst  
    Native vector widths:   char 16, short 8, int 4, long 2
    Preferred vector width: char 16, short 8, int 4, long 2
    Global Memory:          1024.0 MB
    Local Memory:           32.0 KB (Local)
    Max memory alloc. size: 256.2 MB
    Max clock (MHz):        1040
    Max Work Group Size:    256
    Parallel compute cores: 44
    Stream processors:      3520  (44 x 80)
    Speed index:            3660800