give user more control over embedded_start_block.S contents (#2470)

Author: kilograham

src/rp2_common/pico_crt0/embedded_start_block.inc.S

@@ -5,6 +5,21 @@
 #endif
 #endif
 
+#ifndef PICO_CRT0_INCLUDE_PICOBIN_VECTOR_TABLE_ITEM
+// If no_flash bin, then include a vector table item
+#if PICO_NO_FLASH && !PICO_RP2040
+#define PICO_CRT0_INCLUDE_PICOBIN_VECTOR_TABLE_ITEM 1
+#endif
+#endif
+
+#ifndef PICO_CRT0_INCLUDE_PICOBIN_ENTRY_POINT_ITEM
+// On RISC-V the default entry point from bootrom is the start of the binary, but
+// we have our vtable at the start, so we must include an entry point
+#ifdef __riscv
+#define PICO_CRT0_INCLUDE_PICOBIN_ENTRY_POINT_ITEM 1
+#endif
+#endif
+
 #ifndef PICO_CRT0_INCLUDE_PICOBIN_BLOCK
 #define PICO_CRT0_INCLUDE_PICOBIN_BLOCK PICO_CRT0_INCLUDE_PICOBIN_IMAGE_TYPE_ITEM
 #endif
@@ -73,9 +88,7 @@ embedded_block:
 .hword PICO_CRT0_VERSION_MAJOR
 #endif
 
-#ifdef __riscv
-// On RISC-V the default entry point from bootrom is the start of the binary, but
-// we have our vtable at the start, so we must include an entry point
+#if PICO_CRT0_INCLUDE_PICOBIN_ENTRY_POINT_ITEM
 .byte PICOBIN_BLOCK_ITEM_1BS_ENTRY_POINT
 .byte 0x3 // word size to next item
 .byte 0 // pad
@@ -84,15 +97,12 @@ embedded_block:
 .word SRAM_END // stack pointer
 #endif
 
-#if !PICO_RP2040
-#if PICO_NO_FLASH
-// If no_flash bin, then include a vector table item
+#if PICO_CRT0_INCLUDE_PICOBIN_VECTOR_TABLE_ITEM
 .byte PICOBIN_BLOCK_ITEM_1BS_VECTOR_TABLE
 .byte 0x2
 .hword 0
 .word __vectors
 #endif
-#endif
 
 .byte PICOBIN_BLOCK_ITEM_2BS_LAST
 .hword (embedded_block_end - embedded_block - 16 ) / 4 // total size of all
@@ -106,4 +116,4 @@ embedded_block:
 #endif
 .word PICOBIN_BLOCK_MARKER_END
 embedded_block_end:
-#endif
+#endif