building it on Windows with `go get` failed

[EasiestSoft]

# github.com/joway/imagic/vendor/github.com/joway/libimagequant-go/pngquant
blur.c: In function 'liq_max3':
blur.c:91:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
 }
 ^
blur.c: In function 'liq_min3':
blur.c:118:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
 }
 ^
blur.c: In function 'liq_blur':
blur.c:132:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
 }
 ^
# github.com/joway/imagic/vendor/github.com/joway/libimagequant-go/pngquant
kmeans.c: In function 'kmeans_init':
kmeans.c:26:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
 }
 ^
kmeans.c: In function 'kmeans_update_color':
kmeans.c:36:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
 }
 ^
kmeans.c: In function 'kmeans_finalize':
kmeans.c:64:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
 }
 ^
kmeans.c: In function 'kmeans_do_iteration':
kmeans.c:93:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
 }
 ^
# github.com/joway/imagic/vendor/github.com/joway/libimagequant-go/pngquant
mediancut.c: In function 'mediancut':
mediancut.c:409:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
 }
 ^
# github.com/joway/imagic/vendor/github.com/joway/libimagequant-go/pngquant
mempool.c: In function 'mempool_alloc':
mempool.c:61:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
 }
 ^
mempool.c: In function 'mempool_create':
mempool.c:50:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
 }
 ^
mempool.c: In function 'mempool_destroy':
mempool.c:70:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
 }
 ^
# github.com/joway/imagic/vendor/github.com/joway/libimagequant-go/pngquant
nearest.c: In function 'nearest_init':
nearest.c:136:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
 }
 ^
nearest.c: In function 'nearest_search':
nearest.c:190:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
 }
 ^
nearest.c: In function 'nearest_free':
nearest.c:195:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
 }
 ^
# github.com/joway/imagic/vendor/github.com/joway/libimagequant-go/pngquant
pam.c: In function 'pam_add_to_hash':
pam.c:157:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
 }
 ^
pam.c: In function 'pam_computeacolorhash':
pam.c:66:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
 }
 ^
pam.c: In function 'pam_allocacolorhash':
pam.c:177:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
 }
 ^
pam.c: In function 'pam_freeacolorhash':
pam.c:241:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
 }
 ^
pam.c: In function 'pam_freeacolorhist':
pam.c:247:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
 }
 ^
pam.c: In function 'pam_colormap':
pam.c:264:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
 }
 ^
pam.c: In function 'pam_duplicate_colormap':
pam.c:273:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
 }
 ^
pam.c: In function 'pam_freecolormap':
pam.c:278:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
 }
 ^
pam.c: In function 'to_f_set_gamma':
pam.c:285:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
 }
 ^
pam.c: In function 'pam_acolorhashtoacolorhist':
pam.c:233:1: warning: visibility attribute not supported in this configuration; ignored [-Wattributes]
 }
 ^