Relocated the R_ARM_RELATIVE entries when a GNU ThreadX module starts, so a global pointer initialized with the address of another global now holds the loaded address

[fdesbiens]

Fixes #230

The GNU module startup code in gcc_setup.s rebases the GOT and copies the initialized data into the module data area, but it never applies the relocations the linker records for words inside that data. A global initialized with a link time constant, such as char *pBuffer = buffer;, a global function pointer, or a structure member holding the address of a string literal, therefore keeps the address it was linked at and points outside the loaded module.

gcc_setup.s now walks the .rel.dyn table after the data copy and adjusts every R_ARM_RELATIVE entry whose target lies in the module data area, using the same code and data base arithmetic as the existing GOT loop. Entries targeting the read only code area are skipped and a zero value is left alone, exactly as the GOT loop already does. The flash base is reloaded first because crt0_memory_copy uses r3 as a scratch register.

The relocation table is only emitted when the module is linked with -pie, so the example module build scripts now pass -pie --no-dynamic-linker, and the example module linker scripts discard the .dynamic section that -pie would otherwise place at address zero, which inflated the binary image from a few hundred bytes to nearly 200 KB.

A module linked without -pie has an empty relocation table, so the new loop is a no-op and the previous behaviour is preserved exactly.

Changed: gcc_setup.s for Cortex-M3, M4, M7, M33 and M0+, sample_threadx_module.ld for Cortex-M3, M4, M7 and M0+, and build_threadx_module_sample.bat for Cortex-M3, M4 and M7. Cortex-M23 and M33 ship no module linker script or build script, and the Cortex-A35 AArch64 startup code uses a different relocation format, so those are left for a follow up.

Verified on qemu-system-arm with a module linked at one address and loaded at another: a global char pointer, a global function pointer, a global string pointer, and pointer members of a global structure all resolve to the loaded addresses, and the same module linked without -pie still starts and runs.