Add fiber asm for sparc64 and powerpc64, to avoid
"configure: error: setcontext required but not found"

Index: libphobos/configure
--- libphobos/configure.orig
+++ libphobos/configure
@@ -695,6 +695,8 @@ DRUNTIME_CPU_X86_FALSE
 DRUNTIME_CPU_X86_TRUE
 DRUNTIME_CPU_POWERPC_FALSE
 DRUNTIME_CPU_POWERPC_TRUE
+DRUNTIME_CPU_SPARC64_FALSE
+DRUNTIME_CPU_SPARC64_TRUE
 DRUNTIME_CPU_MIPS_FALSE
 DRUNTIME_CPU_MIPS_TRUE
 DRUNTIME_CPU_LOONGARCH_FALSE
@@ -14312,6 +14314,9 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
       powerpc*)
                druntime_target_cpu_parsed="powerpc"
                ;;
+      sparc64)
+               druntime_target_cpu_parsed="sparc64"
+               ;;
       i[34567]86|x86_64)
                druntime_target_cpu_parsed="x86"
                ;;
@@ -14362,6 +14367,14 @@ else
   DRUNTIME_CPU_POWERPC_FALSE=
 fi
 
+   if test "$druntime_target_cpu_parsed" = "sparc64"; then
+  DRUNTIME_CPU_SPARC64_TRUE=
+  DRUNTIME_CPU_SPARC64_FALSE='#'
+else
+  DRUNTIME_CPU_SPARC64_TRUE='#'
+  DRUNTIME_CPU_SPARC64_FALSE=
+fi
+
    if test "$druntime_target_cpu_parsed" = "x86"; then
   DRUNTIME_CPU_X86_TRUE=
   DRUNTIME_CPU_X86_FALSE='#'
@@ -15424,7 +15437,8 @@ fi
     aarch64* | \
     arm* | \
     i[34567]86|x86_64 | \
-    powerpc)
+    sparc64* | \
+    powerpc*)
       druntime_fiber_asm_external=yes
       ;;
   esac
@@ -16067,6 +16081,10 @@ if test -z "${DRUNTIME_CPU_POWERPC_TRUE}" && test -z "
   as_fn_error $? "conditional \"DRUNTIME_CPU_POWERPC\" was never defined.
 Usually this means the macro was only invoked conditionally." "$LINENO" 5
 fi
+if test -z "${DRUNTIME_CPU_SPARC64_TRUE}" && test -z "${DRUNTIME_CPU_SPARC64_FALSE}"; then
+  as_fn_error $? "conditional \"DRUNTIME_CPU_SPARC64\" was never defined.
+Usually this means the macro was only invoked conditionally." "$LINENO" 5
+fi
 if test -z "${DRUNTIME_CPU_X86_TRUE}" && test -z "${DRUNTIME_CPU_X86_FALSE}"; then
   as_fn_error $? "conditional \"DRUNTIME_CPU_X86\" was never defined.
 Usually this means the macro was only invoked conditionally." "$LINENO" 5
