Contents of macro keeps getting indented every time rustfmt runs

[Amanieu]

Possibly related to #1917?

Original:

macro_rules! m {
    () => {
        r#"
            test
        "#
    };
}

After 1 rustfmt:

macro_rules! m {
    () => {
        r#"
                    test
                "#
    };
}

After 2 rustfmt:

macro_rules! m {
    () => {
        r#"
                            test
                        "#
    };
}

[Amanieu]

This bug is still present.

Before:

macro_rules! read_sysreg {
   ($name:ident, $reg:expr, $result:expr) => {
       safe_asm!(
           concat!("mrs $1, ", stringify!($reg)),
           : "=r" ($result)
           :
       )
   };
}

After:

macro_rules! read_sysreg {
    ($name:ident, $reg:expr, $result:expr) => {
        safe_asm!(
                    concat!("mrs $1, ", stringify!($reg)),
                    : "=r" ($result)
                    :
                )
    };
}

[topecongiro]

@Amanieu Thanks for the additional report. This looks like a dup of #2607, would you please try this workaround for now?