libsel4platsupport: Increase starting stack alignment

Whilst _start will align our stack as we are calling C code *before* _start we need
to ensure our stack is 16 byte aligned at those points as well
diff --git a/libsel4platsupport/src/sel4_arch/aarch64/sel4_crt0.S b/libsel4platsupport/src/sel4_arch/aarch64/sel4_crt0.S
index d2acaf5..1801e33 100644
--- a/libsel4platsupport/src/sel4_arch/aarch64/sel4_crt0.S
+++ b/libsel4platsupport/src/sel4_arch/aarch64/sel4_crt0.S
@@ -110,7 +110,7 @@
     .8byte 8 /* p_align set to word alignment */
 
 .bss
-.align  8
+.align  16
 
 _stack_bottom:
 .space  16384
diff --git a/libsel4platsupport/src/sel4_arch/ia32/sel4_crt0.S b/libsel4platsupport/src/sel4_arch/ia32/sel4_crt0.S
index 2adbfc8..ccf98e1 100644
--- a/libsel4platsupport/src/sel4_arch/ia32/sel4_crt0.S
+++ b/libsel4platsupport/src/sel4_arch/ia32/sel4_crt0.S
@@ -117,7 +117,7 @@
     .4byte 4 /* p_align set to word alignment */
 
     .bss
-    .align  8
+    .align  16
 
 _stack_bottom:
     .space  16384
diff --git a/libsel4platsupport/src/sel4_arch/x86_64/sel4_crt0.S b/libsel4platsupport/src/sel4_arch/x86_64/sel4_crt0.S
index ead0c90..b9a8295 100644
--- a/libsel4platsupport/src/sel4_arch/x86_64/sel4_crt0.S
+++ b/libsel4platsupport/src/sel4_arch/x86_64/sel4_crt0.S
@@ -110,7 +110,7 @@
     .8byte 8 /* p_align set to word alignment */
 
     .bss
-    .align  8
+    .align  16
 
 _stack_bottom:
     .space  16384