[kernel] Make panic::panic not inline

Panic is referenced everywhere (mostly through kassert being always
inline). It's also so much easier to breakpoint on panic in GDB this
way.

src/kernel/assert.cpp

@@ -13,6 +13,45 @@ install(uintptr_t entrypoint, util::const_buffer symbol_data)
     symbol_table = symbol_data.pointer;
 }
 
+extern uint32_t *apic_icr;
+extern void const *symbol_table;
+
+[[ noreturn ]]
+void panic(
+        const char *message,
+        const cpu_state *user,
+        const char *function,
+        const char *file,
+        uint64_t line)
+{
+    cpu_data &cpu = current_cpu();
+
+    // Grab the global panic block for ourselves
+    cpu.panic = __atomic_exchange_n(&g_panic_data_p, nullptr, __ATOMIC_ACQ_REL);
+
+    // If we aren't the first CPU to panic, cpu.panic will be null
+    if (cpu.panic) {
+        cpu.panic->symbol_data = symbol_table;
+        cpu.panic->user_state = user;
+
+        cpu.panic->message = message;
+        cpu.panic->function = function;
+        cpu.panic->file = file;
+        cpu.panic->line = line;
+
+        cpu.panic->cpus = g_num_cpus;
+
+        static constexpr uint32_t send_nmi_command =
+            (4 <<  8) | // Delivery mode NMI
+            (1 << 14) | // assert level high
+            (2 << 18);  // destination all
+
+        *apic_icr = send_nmi_command;
+    }
+
+    while (1) asm ("hlt");
+}
+
 } // namespace panic
 
 extern "C"

src/kernel/assert.h

@@ -7,45 +7,13 @@
 
 namespace panic {
 
-constexpr uint32_t send_nmi_command =
-    (4 << 8) |  // Delivery mode NMI
-    (1 << 14) | // assert level high
-    (2 << 18);  // destination all
-
-extern uint32_t *apic_icr;
-extern void const *symbol_table;
-
 [[ noreturn ]]
-__attribute__ ((always_inline))
-inline void panic(
+void panic(
         const char *message = nullptr,
         const cpu_state *user = nullptr,
         const char *function = __builtin_FUNCTION(),
         const char *file = __builtin_FILE(),
-        uint64_t line = __builtin_LINE())
-{
-    cpu_data &cpu = current_cpu();
-
-    // Grab the global panic block for ourselves
-    cpu.panic = __atomic_exchange_n(&g_panic_data_p, nullptr, __ATOMIC_ACQ_REL);
-
-    // If we aren't the first CPU to panic, cpu.panic will be null
-    if (cpu.panic) {
-        cpu.panic->symbol_data = symbol_table;
-        cpu.panic->user_state = user;
-
-        cpu.panic->message = message;
-        cpu.panic->function = function;
-        cpu.panic->file = file;
-        cpu.panic->line = line;
-
-        cpu.panic->cpus = g_num_cpus;
-
-        *apic_icr = send_nmi_command;
-    }
-
-    while (1) asm ("hlt");
-}
+        uint64_t line = __builtin_LINE());
 
 /// Install a panic handler.
 /// \arg entrypoint   Virtual address of the panic handler's entrypoint