Fix NPM clean-cache of nuxeo-platform-spreadsheet under Windows

[INFO] --- maven-antrun-plugin:1.7:run (gulp-build) @ nuxeo-platform-spreadsheet ---
clean-cache:
   [delete] Deleting directory C:\WORK\addons\nuxeo-platform-spreadsheet\src\main\js\node_modules
   [delete] Deleting directory C:\WORK\addons\nuxeo-platform-spreadsheet\src\main\js\app\bower_components

clean-cache:
     [exec] npm ERR! Windows_NT 6.3.9600
     [exec] npm ERR! argv "C:\\Program Files\\nodejs\\node.exe" "C:\\npm\\node_modules\\npm\\bin\\npm-cli.js" "cache" "clean"
     [exec] npm ERR! node v6.9.2
     [exec] npm ERR! npm  v4.0.5
     [exec] npm ERR! path C:\Users\jenkins\AppData\Roaming\npm-cache
     [exec] npm ERR! code EPERM
     [exec] npm ERR! errno -4048
     [exec] npm ERR! syscall rmdir
     [exec] 
     [exec] npm ERR! Error: EPERM: operation not permitted, rmdir 'C:\Users\jenkins\AppData\Roaming\npm-cache'

1 verbose cli [ 'C:\\Program Files\\nodejs\\node.exe',
1 verbose cli   'C:\\npm\\node_modules\\npm\\bin\\npm-cli.js',
1 verbose cli   'cache',
1 verbose cli   'clean' ]
2 info using npm@4.0.5
3 info using node@v6.9.2
4 silly ls normalized .
(...)
1652 silly vacuum-fs quitting because other entries in C:\Users\jenkins\AppData\Roaming\npm-cache
2200 silly vacuum-fs removing C:\Users\jenkins\AppData\Roaming\npm-cache
2201 silly vacuum-fs unable to remove C:\Users\jenkins\AppData\Roaming\npm-cache due to EPERM: operation not permitted, rmdir 'C:\Users\jenkins\AppData\Roaming\npm-cache'
2202 silly vacuum-fs quitting because lost the race to remove C:\Users\jenkins\AppData\Roaming\npm-cache
2748 silly vacuum-fs quitting because other entries in C:\Users\jenkins\AppData\Roaming
2749 verbose stack Error: EPERM: operation not permitted, rmdir 'C:\Users\jenkins\AppData\Roaming\npm-cache'