srcs is updated with the OS-specific path separator

[bartoszpop]

rules_jvm updates the srcs attribute with the OS-specific path separator, which leads to unnecessary updates and the parent path being incorrectly trimmed, e.g. for the following project structure

.
+-- WORKSPACE
+-- BUILD.bazel
+-- project
|   +-- BUILD.bazel
|   +-- src
|       +-- com
|           +-- example
|               +-- SomeClass.java

and the nested BUILD.bazel file having:

java_library(
    name = "some-project",
    srcs = [
        "src/com/example/SomeClass.java"
	]

once "bazel run gazelle" is executed on Windows, it will update the file to:

java_library(
    name = "some-project",
    srcs = [
        "project\\src\\com\\example\\SomeClass.java"
	]

I think it should always use "/" because java_library and other rules that consume this attribute support "/" regardless of the OS they run on.