RECORD file is broken if `strip_path_prefixes` used

[ppodolsky]

Hi! Following rule

py_wheel(
    ...
    strip_path_prefixes = ["prefix"],
)

creates wheel with RECORD file containing following records:

/blabla/__init__.py,sha256=47DEQpj8HBSa-_TImW-5JCeuQeRkm5NMpJWZG3hSuFU,0
/blabla/language_detect.py,sha256=RTufRn4WInDHn_5W4CThkFp6RV0ZYaserNa1rBLJJ-s,445
/blabla/morph.py,sha256=54gzoFL3oJQWq-cKuhJfXojEOU6Knw0ZR4peX8u7zaY,845
/blabla/regex.py,sha256=LqhF6JmKWihvi02XIFMFZOvmzqMxyixIUl1aaYn0BkQ,1488
/blabla/utils.py,sha256=kYW4zrRvksvXzardHjlZgwOLCPJrfVjG72k-gmIqzf4,2726
package-1.0.4.dist-info/METADATA,sha256=ogEnrEFMwzwSuA9V_uCzMViGbgnxb-UQDHLatLVBUgM,462
package-1.0.4.dist-info/RECORD,,
package-1.0.4.dist-info/WHEEL,sha256=sobxWSyDDkdg_rinUth-jxhXHqoNqlmNMJY3aTZn2Us,91

The issue is that remaining leading slash in first files break the package. If you will try to install such wheel with requirement it failes at
https://github.com/pypa/installer/blob/main/src/installer/sources.py#L158
The solution is to merely lstrip this slash for every line in RECORD