Fix GDBstub linkage options

GDB works with pure GNU GCC and pure GNU binutils now.  Still warnings
galore, but tested with the example sketch in the docs.

Author: earlephilhower

libraries/GDBStub/src/internal/gdbstub.c

@@ -900,7 +900,7 @@ void ATTR_GDBINIT gdbstub_set_uart_isr_callback(void (*func)(void*, uint8_t), vo
 
 
 //gdbstub initialization routine.
-void ATTR_GDBINIT gdbstub_init() {
+void gdbstub_init() {
 #if GDBSTUB_REDIRECT_CONSOLE_OUTPUT
 	os_install_putc1(gdbstub_semihost_putchar1);
 #endif
@@ -923,4 +923,4 @@ bool ATTR_GDBEXTERNFN gdb_present() {
 }
 
 void ATTR_GDBFN gdb_do_break() { gdbstub_do_break(); }
-void ATTR_GDBINIT gdb_init() __attribute__((alias("gdbstub_init")));
+void gdb_init() __attribute__(( alias("gdbstub_init") ));

tools/sdk/ld/eagle.app.v6.common.ld.h

@@ -129,6 +129,8 @@ SECTIONS
 
     *(.text.app_entry*)  /* The main startup code */
 
+    *(.text.gdbstub*, .text.gdb_init)    /* Any GDB hooks */
+
     /* all functional callers are placed in IRAM (including SPI/IRQ callbacks/etc) here */
     *(.text._ZNKSt8functionIF*EE*)  /* std::function<any(...)>::operator()() const */
   } >iram1_0_seg :iram1_0_phdr