use __builtin_alloca, drop non-standard alloca.h

[Jeff Law]

On 8/15/19 2:17 AM, Alexandre Oliva wrote:
> Since alloca.h is not ISO C, most of our alloca-using tests seem to
> rely on __builtin_alloca instead of including the header and calling
> alloca.  This patch extends this practice to some of the exceptions I
> found in gcc.target, marking them as requiring a functional alloca
> while at that.
> 
> Tested on x86_64-linux-gnu, and manually compile-tested the non-x86
> tests.  Ok to install?
> 
> 
> for  gcc/testsuite/ChangeLog
> 
> 	* gcc.target/arc/interrupt-6.c: Use __builtin_alloca, require
> 	effective target support for alloca, drop include of alloca.h.
> 	* gcc.target/i386/pr80969-3.c: Likewise.
> 	* gcc.target/sparc/setjmp-1.c: Likewise.
> 	* gcc.target/x86_64/abi/ms-sysv/gen.cc: Likewise.
> 	* gcc.target/x86_64/abi/ms-sysv/ms-sysv.c: Likewise.
OK
jeff