Upgrade to GDB 15.1

The only relevant changes for w64dk are in the Debugger Adapter
Protocol: process event, cancel request, attach request, and
dap-log-level configuration.

Dockerfile

@@ -7,7 +7,7 @@ ARG BUSYBOX_VERSION=FRP-5398-g89ae34445
 ARG CTAGS_VERSION=6.0.0
 ARG EXPAT_VERSION=2.6.2
 ARG GCC_VERSION=14.1.0
-ARG GDB_VERSION=14.2
+ARG GDB_VERSION=15.1
 ARG GMP_VERSION=6.3.0
 ARG LIBICONV_VERSION=1.17
 ARG MAKE_VERSION=4.4.1

src/SHA256SUMS

@@ -3,7 +3,7 @@ e366f887a56bf6f64adff15b7b08ba487fea14c121045078437abe7217cf060d  busybox-w32-FR
 71229a73f25529c9e3dabb2cb7310c55405d31caee8e8a9ab5c71b2406d4005a  ctags-6.0.0.tar.gz
 ee14b4c5d8908b1bec37ad937607eab183d4d9806a08adee472c3c3121d27364  expat-2.6.2.tar.xz
 e283c654987afe3de9d8080bc0bd79534b5ca0d681a73a11ff2b5d3767426840  gcc-14.1.0.tar.xz
-2d4dd8061d8ded12b6c63f55e45344881e8226105f4d2a9b234040efa5ce7772  gdb-14.2.tar.xz
+38254eacd4572134bca9c5a5aa4d4ca564cbbd30c369d881f733fb6b903354f2  gdb-15.1.tar.xz
 a3c2b80201b89e68616f4ad30bc66aee4927c3ce50e33929ca819d5c43538898  gmp-6.3.0.tar.xz
 8f74213b56238c85a50a5329f77e06198771e70dd9a739779f4c02f65d971313  libiconv-1.17.tar.gz
 dd16fb1d67bfab79a72f5e8390735c49e3e8e70b4945a15ab1f81ddb78658fb3  make-4.4.1.tar.gz

src/gdb-000-alternate-main.patch

@@ -1,10 +1,10 @@
 --- a/gdb/symtab.c
 +++ b/gdb/symtab.c
-@@ -6314,6 +6314,23 @@
+@@ -6537,6 +6537,23 @@
    if (symbol_found_p)
      return;
 
-+  if (gdbarch_osabi (target_gdbarch ()) == GDB_OSABI_WINDOWS)
++  if (gdbarch_osabi (current_inferior ()->arch ()) == GDB_OSABI_WINDOWS)
 +    {
 +      static const char *const mains[] = {
 +	"WinMain", "wWinMain", "main", "wmain", "WinMainCRTStartup", "mainCRTStartup"