Add continuous integration on Windows about cxx HOT 6 CLOSED

$ cargo run --manifest-path demo-rs/Cargo.toml
info: default toolchain set to 'nightly'
info: syncing channel updates for 'nightly-x86_64-pc-windows-gnu'
   Compiling proc-macro2 v1.0.8
   Compiling unicode-xid v0.2.0
   Compiling winapi-x86_64-pc-windows-gnu v0.4.0
   Compiling cc v1.0.50
   Compiling syn v1.0.14
   Compiling winapi v0.3.8
   Compiling anyhow v1.0.26
   Compiling unicode-segmentation v1.6.0
   Compiling unicode-width v0.1.7
   Compiling codespan v0.7.0
   Compiling link-cplusplus v1.0.1
   Compiling cxx v0.1.2 (C:\Users\travis\build\dtolnay\cxx)
   Compiling quote v1.0.2
   Compiling winapi-util v0.1.3
   Compiling termcolor v1.1.0
   Compiling codespan-reporting v0.7.0
   Compiling thiserror-impl v1.0.11
   Compiling cxxbridge-macro v0.1.2 (C:\Users\travis\build\dtolnay\cxx\macro)
error[E0583]: file not found for module `syntax`
  --> macro\src\lib.rs:13:5
   |
13 | mod syntax;
   |     ^^^^^^
   |
   = help: name the file either syntax.rs or syntax\mod.rs inside the directory "macro\src"

error: aborting due to previous error

For more information about this error, try `rustc --explain E0583`.
error: could not compile `cxxbridge-macro`.

$ cargo run --manifest-path demo-rs/Cargo.toml

error: failed to run custom build command for `cxxbridge-demo v0.0.0 (C:\Users\travis\build\dtolnay\cxx\demo-rs)`

Caused by:
  process didn't exit successfully: `C:\Users\travis\build\dtolnay\cxx\target\debug\build\cxxbridge-demo-7cfe4801d6523f80\build-script-build` (exit code: 1)
--- stdout
TARGET = Some("x86_64-pc-windows-gnu")
OPT_LEVEL = Some("0")
HOST = Some("x86_64-pc-windows-gnu")
CC_x86_64-pc-windows-gnu = None
CC_x86_64_pc_windows_gnu = None
HOST_CC = None
CC = None
CFLAGS_x86_64-pc-windows-gnu = None
CFLAGS_x86_64_pc_windows_gnu = None
HOST_CFLAGS = None
CFLAGS = None
CRATE_CC_NO_DEFAULTS = None
DEBUG = Some("true")
CARGO_CFG_TARGET_FEATURE = Some("fxsr,mmx,sse,sse2")
running: "gcc.exe" "-O0" "-ffunction-sections" "-fdata-sections" "-g" "-fno-omit-frame-pointer" "-m64" "-I" "\\\\?\\C:\\Users\\travis\\build\\dtolnay\\cxx\\target\\cxxbridge" "-I" "\\\\?\\C:\\Users\\travis\\build\\dtolnay\\cxx" "-Wall" "-Wextra" "-std=c++11" "-o" "C:\\Users\\travis\\build\\dtolnay\\cxx\\target\\debug\\build\\cxxbridge-demo-0333a5c7c738fe49\\out\\demo-rs\\src\\main.rs.o" "-c" "C:\\Users\\travis\\build\\dtolnay\\cxx\\target\\debug\\build\\cxxbridge-demo-0333a5c7c738fe49\\out\\demo-rs\\src\\main.rs.cc"
cargo:warning=C:\Users\travis\build\dtolnay\cxx\target\debug\build\cxxbridge-demo-0333a5c7c738fe49\out\demo-rs\src\main.rs.cc:1:10: fatal error: demo-cxx/demo.h: No such file or directory
cargo:warning= #include "demo-cxx/demo.h"
cargo:warning=          ^~~~~~~~~~~~~~~~~
cargo:warning=compilation terminated.
exit code: 1