Genode platform fixes (#17521)

* Genode: move dyncall failures to runtime

Do not use the "error" pragma to warn that dynamic library loading is
not implemented, print a message at runtime and exit.

* Genode: use stricter dataspace type in page allocator

* Genode: remove compiler configuration from nim.cfg

Self-hosting Nim is not supported on Genode and defining the
cross-compilation environment can be done externally.

* Genode: use new mutex API

* Genode: call nim_component_construct as a C procedure

* Genode: implement echo for NimStringV2

config/nim.cfg

@@ -114,7 +114,7 @@ nimblepath="$home/.nimble/pkgs/"
     clang.options.linker = "-Wl,--as-needed -lnetwork"
     clang.cpp.options.linker = "-Wl,--as-needed -lnetwork"
     tcc.options.linker = "-Wl,--as-needed -lnetwork"
-  @else:
+  @elif not genode:
     # -fopenmp
     gcc.options.linker = "-ldl"
     gcc.cpp.options.linker = "-ldl"
@@ -289,29 +289,6 @@ vcc.cpp.options.size = "/O1"
 # Configuration for the Tiny C Compiler:
 tcc.options.always = "-w"
 
-# Configuration for the Genode toolchain
-@if genode:
-  noCppExceptions # avoid std C++
-  tlsEmulation:on # no TLS segment register magic
-  @if i386 or amd64:
-    gcc.exe = "genode-x86-gcc"
-    gcc.cpp.exe = "genode-x86-g++"
-    gcc.cpp.linkerexe = "genode-x86-ld"
-  @elif arm:
-    gcc.exe = "genode-arm-gcc"
-    gcc.cpp.exe = "genode-arm-g++"
-    gcc.cpp.linkerexe = "genode-arm-ld"
-  @elif arm64:
-    gcc.exe = "genode-aarch64-gcc"
-    gcc.cpp.exe = "genode-aarch64-g++"
-    gcc.cpp.linkerexe = "genode-aarch64-ld"
-  @elif riscv64:
-    gcc.exe = "genode-riscv-gcc"
-    gcc.cpp.exe = "genode-riscv-g++"
-    gcc.cpp.linkerexe = "genode-riscv-ld"
-  @end
-@end
-
 @if arm or arm64:
   --define:nimEmulateOverflowChecks
 @end