Hi,
GNU Automake will generate a broken Makefile when configuring if some variables
containing line
breaks.
If variable A is defined as:
```autoconf
A=$(cat a.txt)`
AC_SUBST([A])
```
And `a.txt` contains:
```text
line 1
line 2
```
Then the generated `Makefile.in` will contain:
```makefile
Hi,
I would like to report one quite annoying issue related to Automake's `compile`
wrapper when it is used with `cl.exe` to compile some C++ files from Msys2.
I was building some GNU packages with MSVC's `cl.exe`, and compilation of some
C++ source files was failing with `cl.exe` reporting non
