auto merge of #16691 : klutzy/rust/issue-15297, r=alexcrichton

First commit fixes issue regarding recognizing MSYS2 build.
Second commit fixes issue regarding MSYS/Windows paths.

README.md

@@ -71,7 +71,7 @@ To easily build on windows we can use [MSYS2](http://sourceforge.net/projects/ms
 3. With that now start `mingw32_shell.bat` from where you installed MSYS2 (i.e. `C:\msys`).
 4. From there just navigate to where you have Rust's source code, configure and build it:
 
-        $ ./configure --build=i686-pc-mingw32
+        $ ./configure
         $ make && make install
 
 [repo]: https://github.com/rust-lang/rust

configure

@@ -299,13 +299,19 @@ case $CFG_OSTYPE in
         CFG_OSTYPE=apple-darwin
         ;;
 
-    MINGW32*)
+    MINGW*)
+        # msys' `uname` does not print gcc configuration, but prints msys
+        # configuration. so we cannot believe `uname -m`:
+        # msys1 is always i686 and msys2 is always x86_64.
+        # instead, msys defines $MSYSTEM which is MINGW32 on i686 and
+        # MINGW64 on x86_64.
+        CFG_CPUTYPE=i686
         CFG_OSTYPE=pc-mingw32
-        ;;
-
-    MINGW64*)
-        # msys2, MSYSTEM=MINGW64
-        CFG_OSTYPE=w64-mingw32
+        if [ "$MSYSTEM" = MINGW64 ]
+        then
+            CFG_CPUTYPE=x86_64
+            CFG_OSTYPE=w64-mingw32
+        fi
         ;;
 
 # Thad's Cygwin identifers below

src/etc/maketest.py

@@ -15,13 +15,14 @@ import sys
 # msys1/msys2 automatically converts `/abs/path1:/abs/path2` into
 # `c:\real\abs\path1;c:\real\abs\path2` (semicolons) if shell thinks
 # the value is list of paths.
+# (if there is only one path, it becomes `c:/real/abs/path`.)
 # this causes great confusion and error: shell and Makefile doesn't like
 # windows paths so it is really error-prone. revert it for peace.
 def normalize_path(v):
-    # c:\path -> /c/path
-    if ':\\' in v:
-        v = '/' + v.replace(':\\', '/')
     v = v.replace('\\', '/')
+    # c:/path -> /c/path
+    if ':/' in v:
+        v = '/' + v.replace(':/', '/')
     return v