[builtins] Fix divtc3.c etc. compilation on Solaris/SPARC with gcc (llvm#101662)

`compiler-rt/lib/builtins/divtc3.c` and `multc3.c` don't compile on
Solaris/sparcv9 with `gcc -m32`:
```
FAILED: projects/compiler-rt/lib/builtins/CMakeFiles/clang_rt.builtins-sparc.dir/divtc3.c.o
[...]
compiler-rt/lib/builtins/divtc3.c: In function ‘__divtc3’:
compiler-rt/lib/builtins/divtc3.c:22:18: error: implicit declaration of function ‘__compiler_rt_logbtf’ [-Wimplicit-function-declaration]
   22 |   fp_t __logbw = __compiler_rt_logbtf(
      |                  ^~~~~~~~~~~~~~~~~~~~
```
and many more. It turns out that while the definition of `__divtc3` is
guarded with `CRT_HAS_F128`, the `__compiler_rt_logbtf` and other
declarations use `CRT_HAS_128BIT && CRT_HAS_F128` as guard. This only
shows up with `gcc` since, as documented in Issue llvm#41838, `clang`
violates the SPARC psABI in not using 128-bit `long double`, so this
code path isn't used.

Fixed by changing the guards to match.

Tested on `sparcv9-sun-solaris2.11`.

Author: rorth

compiler-rt/lib/builtins/divtc3.c

@@ -13,7 +13,7 @@
 #define QUAD_PRECISION
 #include "fp_lib.h"
 
-#if defined(CRT_HAS_F128)
+#if defined(CRT_HAS_128BIT) && defined(CRT_HAS_F128)
 
 // Returns: the quotient of (a + ib) / (c + id)
 

compiler-rt/lib/builtins/multc3.c

@@ -15,7 +15,7 @@
 #include "int_lib.h"
 #include "int_math.h"
 
-#if defined(CRT_HAS_F128)
+#if defined(CRT_HAS_128BIT) && defined(CRT_HAS_F128)
 
 // Returns: the product of a + ib and c + id