Add some endbr64 instructions: required for rustc binary on amd64 with IBT.

Index: vendor/psm-0.1.26/src/arch/x86_64.s
--- vendor/psm-0.1.26/src/arch/x86_64.s.orig
+++ vendor/psm-0.1.26/src/arch/x86_64.s
@@ -26,6 +26,7 @@ TYPE(rust_psm_stack_direction)
 FUNCTION(rust_psm_stack_direction):
 /* extern "sysv64" fn() -> u8 (%al) */
 .cfi_startproc
+    endbr64
     movb $STACK_DIRECTION_DESCENDING, %al # always descending on x86_64
     retq
 END_FUNCTION(rust_psm_stack_direction)
@@ -38,6 +39,7 @@ TYPE(rust_psm_stack_pointer)
 FUNCTION(rust_psm_stack_pointer):
 /* extern "sysv64" fn() -> *mut u8 (%rax) */
 .cfi_startproc
+    endbr64
     leaq 8(%rsp), %rax
     retq
 .rust_psm_stack_pointer_end:
@@ -57,6 +59,7 @@ FUNCTION(rust_psm_replace_stack):
     8-byte offset necessary to account for the "return" pointer that would otherwise be placed onto
     stack with a regular call
 */
+    endbr64
     leaq -8(%rdx), %rsp
     jmpq *%rsi
 .rust_psm_replace_stack_end:
@@ -70,6 +73,7 @@ TYPE(rust_psm_on_stack)
 FUNCTION(rust_psm_on_stack):
 /* extern "sysv64" fn(%rdi: usize, %rsi: usize, %rdx: extern "sysv64" fn(usize, usize), %rcx: *mut u8) */
 .cfi_startproc
+    endbr64
     pushq %rbp
     .cfi_def_cfa %rsp, 16
     .cfi_offset %rbp, -16
