[gcc r12-6159] libgfortran: Fix bootstrap on targets without static_assert macro.

[Iain D Sandoe <iains@gcc.gnu.org>]

https://gcc.gnu.org/g:e3cbb8c66c930ba738674b0fcf29848dc3ecfef2

commit r12-6159-ge3cbb8c66c930ba738674b0fcf29848dc3ecfef2
Author: Iain Sandoe <iain@sandoe.co.uk>
Date:   Fri Dec 31 11:52:22 2021 +0000

    libgfortran: Fix bootstrap on targets without static_assert macro.
    
    Although we build the library with GCC which is known to support
    _Static_assert this might be done on a system without the macro
    mapping static_assert to the compiler keyword.
    
    The use of static_assert introduced with r12-6126-g3430132f3e82
    causes bootstrap to fail on such targets, fixed by using the keyword
    directly.
    
    Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>
    
    libgfortran/ChangeLog:
    
            * runtime/string.c (gfc_itoa): Use _Static_assert directly
            instead of via the static_assert macro.

Diff:
---
 libgfortran/runtime/string.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libgfortran/runtime/string.c b/libgfortran/runtime/string.c
index 21585f48dc9..5bc202320c0 100644
--- a/libgfortran/runtime/string.c
+++ b/libgfortran/runtime/string.c
@@ -242,8 +242,8 @@ gfc_itoa (GFC_UINTEGER_LARGEST n, char *buffer, size_t len)
 	 integers (we would need three calls), but they do suffice for all
 	 values up to 2^127, which is the largest that Fortran can produce
 	 (-HUGE(0_16)-1) with its signed integer types.  */
-      static_assert(sizeof(GFC_UINTEGER_LARGEST) <= 2 * sizeof(uint64_t),
-		    "integer too large");
+      _Static_assert (sizeof(GFC_UINTEGER_LARGEST) <= 2 * sizeof(uint64_t),
+		      "integer too large");
 
       GFC_UINTEGER_LARGEST r;
       r = n % TEN19;