Fixes for metal backend

[thilinarmtb]

Description

Trying to get the Metal backend tests pass on my M2.
The following tests fail as of now:

• 5 - bin-c-kernel (SEGFAULT)
• 10 - bin-core-kernel (SEGFAULT)
• 16 - bin-functional-array (Subprocess aborted)
• 17 - bin-functional-range (Subprocess aborted)
• 55 - bin-loops-forLoop (SEGFAULT)

[thilinarmtb]

Seems like these test failures happen even with the Serial backend on M2.

[thilinarmtb]

I am investigating the failure of 5-bin-c-kernel. Seems like if the generated
C source for argKernel (tests/files/argKernel.okl) has the following
function signature, the execution fails on M2 with the serial backend.

extern "C" void argKernel(void *nullPtr, int *mem, char &i8,
                            unsigned char &u8, short &i16, unsigned short &u16,
                            int &i32, unsigned int &u32, long int &i64,
                            unsigned long int &u64, float &f, double &d,
                            mystruct &xy, const char *str);

Instead, if it has the following (without references), I could get it to work with
dlopen() + dlsym().

extern "C" void argKernel(void *nullPtr, int *mem, char i8, unsigned char u8,
                            short i16, unsigned short u16, int i32,
                            unsigned int u32, long int i64,
                            unsigned long int u64, float f, double d,
                            mystruct xy, const char *str);