Hack to remove reference to the (glibc only) symbols __libc_csu_init
and __libc_csu_fini. They are the libc initialize and finish function
pointers. Not sure if this actually works, or if calling the pointers
to be stored there before/after the call to PASCALMAIN is required.

--- fpcsrc/rtl/linux/x86_64/cprt0.as	2015-12-16 16:28:03.000000000 +0100
+++ fpcsrc/rtl/linux/x86_64/cprt0.as	2018-01-02 14:41:08.598952141 +0100
@@ -63,9 +63,10 @@
 	pushq %rsp
 
 	/* Pass address of our own entry points to .fini and .init.  */
-	movq __libc_csu_init@GOTPCREL(%rip), %rcx
-	movq __libc_csu_fini@GOTPCREL(%rip), %r8
-
+/*	not availble in musl libc
+ *	movq __libc_csu_init@GOTPCREL(%rip), %rcx
+ *	movq __libc_csu_fini@GOTPCREL(%rip), %r8
+ */
 	movq main_stub@GOTPCREL(%rip), %rdi
 
 	/* Call the user's main function, and exit with its value.