runtime_loader: Randomly position only relocatable code

The use of an unreliable test for relocatability effectively broke
runtime_loader's support for non-position-independent executables, as it
would insist on randomly positioning these files' segments in memory
anyway causing the program to quickly crash.

With this change runtime_loader uses the object type specified in the
file's header to determine whether its segments can be safely relocated,
restoring support for non-PI executables.

Fixes #12427.

Signed-off-by: Adrien Destugues <[email protected]>

headers/private/system/elf_common.h

@@ -31,6 +31,17 @@
 #define EI_VERSION	6
 #define EI_PAD		7
 
+// e_type (Object file type)
+#define ET_NONE			0 // No file type
+#define ET_REL			1 // Relocatable file
+#define ET_EXEC			2 // Executable file
+#define ET_DYN			3 // Shared object file
+#define ET_CORE			4 // Core file
+#define ET_LOOS			0xfe00 // OS-specific range start
+#define ET_HIOS			0xfeff // OS-specific range end
+#define ET_LOPROC		0xff00 // Processor-specific range start
+#define ET_HIPROC		0xffff // Processor-specific range end
+
 // e_machine (Architecture)
 #define EM_NONE			0 // No machine
 #define EM_M32			1 // AT&T WE 32100