Generate system image with PyCall in "PyJulia-mode"

[tkf]

closes #217

This requires:

• PyCall release with Make PyCall.jl AOT-compilable PyCall.jl#651
• ideally Suggestion: Use different precompilation cache path for different system image JuliaLang/julia#29914 and Request: Add an API for configuring julia_cmd JuliaLang/julia#30065; but it turned out we can gorilla patch them while compiling the system image 41df92e
• Remove [DO NOT MERGE] commits

[tkf]

At the moment, this script fails with:

$ python3 -m julia.build_sys_a sys.a
Invalid bitcast
  %56 = bitcast i64 %55 to %jl_value_t addrspace(64)*, !dbg !409736
LLVM ERROR: Broken function found, compilation aborted!

Edit: it's JuliaLang/julia#31473

[tkf]

Turning off Draft mode to run Travis CI. Still not ready for merge.

[coveralls]

Pull Request Test Coverage Report for Build 648

• 40 of 103 (38.83%) changed or added relevant lines in 3 files are covered.
• 39 unchanged lines in 4 files lost coverage.
• Overall coverage decreased (-4.5%) to 72.323%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/julia/tools.py	3	13	23.08%
src/julia/julia_py.py	13	37	35.14%
src/julia/sysimage.py	24	53	45.28%

Files with Coverage Reduction	New Missed Lines	%
src/julia/ipy/monkeypatch_completer.py	1	58.0%
src/julia/options.py	6	94.12%
src/julia/pytestplugin.py	15	52.63%
src/julia/core.py	17	76.18%

Totals
Change from base Build 637:	-4.5%
Covered Lines:	959
Relevant Lines:	1326

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 648

• 40 of 103 (38.83%) changed or added relevant lines in 3 files are covered.
• 39 unchanged lines in 4 files lost coverage.
• Overall coverage decreased (-4.5%) to 72.323%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/julia/tools.py	3	13	23.08%
src/julia/julia_py.py	13	37	35.14%
src/julia/sysimage.py	24	53	45.28%

Files with Coverage Reduction	New Missed Lines	%
src/julia/ipy/monkeypatch_completer.py	1	58.0%
src/julia/options.py	6	94.12%
src/julia/pytestplugin.py	15	52.63%
src/julia/core.py	17	76.18%

Totals
Change from base Build 637:	-4.5%
Covered Lines:	959
Relevant Lines:	1326

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 648

• 40 of 103 (38.83%) changed or added relevant lines in 3 files are covered.
• 39 unchanged lines in 4 files lost coverage.
• Overall coverage decreased (-4.5%) to 72.323%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/julia/tools.py	3	13	23.08%
src/julia/julia_py.py	13	37	35.14%
src/julia/sysimage.py	24	53	45.28%

Files with Coverage Reduction	New Missed Lines	%
src/julia/ipy/monkeypatch_completer.py	1	58.0%
src/julia/options.py	6	94.12%
src/julia/pytestplugin.py	15	52.63%
src/julia/core.py	17	76.18%

Totals
Change from base Build 637:	-4.5%
Covered Lines:	959
Relevant Lines:	1326

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 707

• 113 of 136 (83.09%) changed or added relevant lines in 6 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+1.09%) to 83.392%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/julia/julia_py.py	35	37	94.59%
src/julia/tools.py	9	13	69.23%
src/julia/sysimage.py	50	67	74.63%

Totals
Change from base Build 701:	1.09%
Covered Lines:	1647
Relevant Lines:	1975

---

💛 - Coveralls

[tkf]

It looks like building the system image on AppVeyor fails due to LLVM ERROR: out of memory:

LLVM ERROR: out of memory\r\n\r\nThis application has requested the Runtime to terminate it in an unusual way.\nPlease contact the application's support team for more information.\r\n\r\nsignal (22): SIGABRT\r\nin expression starting at no file:0\r\nraise at C:\\windows\\SYSTEM32\\msvcrt.dll (unknown line)\r\nabort at C:\\windows\\SYSTEM32\\msvcrt.dll (unknown line)\r\n__ZN4llvm22report_bad_alloc_errorEPKcb at C:\\projects\\julia\\bin\\LLVM.dll (unknown line)\r\nAllocations: 66446306 (Pool: 66440103; Big: 6203); GC: 340

-- https://ci.appveyor.com/project/Keno/pyjulia/builds/23790434/job/8p8hyxeceei0sq3l

Another example: https://ci.appveyor.com/project/Keno/pyjulia/builds/23789506/job/oy06nf93o5xca4l2

(Aside: The output in Captured stderr call is awful. It seems to mix \n and \r\n. Maybe that's why the output is printed like this?)