rust / build: make install should use explicit permissions when creating directories

Closes #10046
Fire fewer homing missiles

This optimizes the `home_for_io` code path by requiring fewer scheduler
operations in some situtations.

When moving to your home scheduler, this no longer forces a context switch if
you're already on the home scheduler. Instead, the homing code now simply pins
you to your current scheduler (making it so you can't be stolen away). If you're
not on your home scheduler, then we context switch away, sending you to your
home scheduler.

When the I/O operation is done, then we also no longer forcibly trigger a
context switch. Instead, the action is cased on whether the task is homed or
not. If a task does not have a home, then the task is re-flagged as not having a
home and no context switch is performed. If a task is homed to the current
scheduler, then we don't do anything, and if the task is homed to a foreign
scheduler, then it's sent along its merry way.

I verified that there are about a third as many `write` syscalls done in print
operations now. Libuv uses write to implement async handles, and the homing
before and after each I/O operation was triggering a write on these async
handles. Additionally, using the terrible benchmark of printing 10k times in a
loop, this drives the runtime from 0.6s down to 0.3s (yay!).
Remove ancient emacs mode lines from test cases

These are relics that serve no purpose.
Point gyp submodule toward github
auto merge of #10082 : brson/rust/gyp, r=huonw

The upstream repo has been offline for hours. A single point of failure is plenty.
auto merge of #10070 : alexcrichton/rust/fewer-missiles, r=brson

This optimizes the `home_for_io` code path by requiring fewer scheduler
operations in some situtations.

When moving to your home scheduler, this no longer forces a context switch if
you're already on the home scheduler. Instead, the homing code now simply pins
you to your current scheduler (making it so you can't be stolen away). If you're
not on your home scheduler, then we context switch away, sending you to your
home scheduler.

When the I/O operation is done, then we also no longer forcibly trigger a
context switch. Instead, the action is cased on whether the task is homed or
not. If a task does not have a home, then the task is re-flagged as not having a
home and no context switch is performed. If a task is homed to the current
scheduler, then we don't do anything, and if the task is homed to a foreign
scheduler, then it's sent along its merry way.

I verified that there are about a third as many `write` syscalls done in print
operations now. Libuv uses write to implement async handles, and the homing
before and after each I/O operation was triggering a write on these async
handles. Additionally, using the terrible benchmark of printing 10k times in a
loop, this drives the runtime from 0.6s down to 0.3s (yay!).
auto merge of #10048 : ibukanov/rust/mkdir-fix, r=brson

The patch replaces mkdir -p dir with (umask 022 && mkdir -p dir). Sadly mkdir -m 755 -p dir does not work if it creates parent directories as those parents will have umask permissions, not the one passed with -m option.   

Closes #10046
auto merge of #10072 : brson/rust/modelines, r=thestinger

These are relics that serve no purpose.
copy_file returns false if source is a directory, or if source and destination are the same.

cc #9947
Added unit tests for modified copy_file()