analyzer: Use __builtin_alloca in gcc.dg/analyzer/call-summaries-2.c

analyzer: Use __builtin_alloca in gcc.dg/analyzer/call-summaries-2.c

gcc.dg/analyzer/call-summaries-2.c currently FAILs on Solaris:

FAIL: gcc.dg/analyzer/call-summaries-2.c (test for excess errors)

Excess errors:
/vol/gcc/src/hg/master/local/gcc/testsuite/gcc.dg/analyzer/call-summaries-2.c:468:12:
warning: implicit declaration of function 'alloca' [-Wimplicit-function-declaration]
/vol/gcc/src/hg/master/local/gcc/testsuite/gcc.dg/analyzer/call-summaries-2.c:468:12:
warning: incompatible implicit declaration of built-in function 'alloca' [-Wbuiltin-declaration-mismatch]

alloca is only declared in <alloca.h>, which isn't included indirectly
anywhere.  To avoid this, I switched the test to use __builtin_alloca
instead, following the vast majority of analyzer tests that use alloca.

Tested no i386-pc-solaris2.11, sparc-sun-solaris2.11, and
x86_64-pc-linux-gnu.

2022-11-23  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>

	gcc/testsuite:
	* gcc.dg/analyzer/call-summaries-2.c (uses_alloca): Use
	__builtin_alloca instead of alloca.