Fix DT_DEBUG handling on MIPS in musl libc.
With this change gdb will load the symbol files for shared libraries on MIPS too.

This patch was taken from this thread: https://www.openwall.com/lists/musl/2022/01/09/4

--- a/arch/mips/reloc.h
+++ b/arch/mips/reloc.h
@@ -29,6 +29,7 @@
 
 #define NEED_MIPS_GOT_RELOCS 1
 #define DT_DEBUG_INDIRECT DT_MIPS_RLD_MAP
+#define DT_DEBUG_INDIRECT_REL DT_MIPS_RLD_MAP_REL
 #define ARCH_SYM_REJECT_UND(s) (!((s)->st_other & STO_MIPS_PLT))
 
 #define CRTJMP(pc,sp) __asm__ __volatile__( \
--- a/arch/mips64/reloc.h
+++ b/arch/mips64/reloc.h
@@ -38,6 +38,7 @@
 
 #define NEED_MIPS_GOT_RELOCS 1
 #define DT_DEBUG_INDIRECT DT_MIPS_RLD_MAP
+#define DT_DEBUG_INDIRECT_REL DT_MIPS_RLD_MAP_REL
 #define ARCH_SYM_REJECT_UND(s) (!((s)->st_other & STO_MIPS_PLT))
 
 #define CRTJMP(pc,sp) __asm__ __volatile__( \
--- a/arch/mipsn32/reloc.h
+++ b/arch/mipsn32/reloc.h
@@ -29,6 +29,7 @@
 
 #define NEED_MIPS_GOT_RELOCS 1
 #define DT_DEBUG_INDIRECT DT_MIPS_RLD_MAP
+#define DT_DEBUG_INDIRECT_REL DT_MIPS_RLD_MAP_REL
 #define ARCH_SYM_REJECT_UND(s) (!((s)->st_other & STO_MIPS_PLT))
 
 #define CRTJMP(pc,sp) __asm__ __volatile__( \
--- a/ldso/dynlink.c
+++ b/ldso/dynlink.c
@@ -1923,6 +1923,10 @@ void __dls3(size_t *sp, size_t *auxv)
 			size_t *ptr = (size_t *) app.dynv[i+1];
 			*ptr = (size_t)&debug;
 		}
+		if (app.dynv[i]==DT_DEBUG_INDIRECT_REL) {
+			size_t *ptr = (size_t *)((size_t)&app.dynv[i] + app.dynv[i+1]);
+			*ptr = (size_t)&debug;
+		}
 	}
 
 	/* This must be done before final relocations, since it calls
--- a/src/internal/dynlink.h
+++ b/src/internal/dynlink.h
@@ -92,6 +92,10 @@ struct fdpic_dummy_loadmap {
 #define DT_DEBUG_INDIRECT 0
 #endif
 
+#ifndef DT_DEBUG_INDIRECT_REL
+#define DT_DEBUG_INDIRECT_REL 0
+#endif
+
 #define AUX_CNT 32
 #define DYN_CNT 32