cmake: initial support for shared vhex library

Using the previously-tested trick with `ld -shared`.

CMakeLists.txt

@@ -6,7 +6,7 @@ set(CMAKE_INSTALL_MESSAGE LAZY)
 # Options
 
 # * -DFXLIBC_TARGET=<vhex-sh, vhex-x86, casiowin-fx, casiowin-cg, gint>
-# * -DSHARED
+# * -DFXLIBC_SHARED=1
 
 option(SHARED "Build a shared library")
 option(STANDARD_NAMESPACE "Use libc.a and put headers in global include folder")
@@ -20,12 +20,14 @@ if(FXLIBC_TARGET STREQUAL vhex-sh)
   list(APPEND TARGET_FOLDERS vhex-generic sh-generic)
   set(FXLIBC_ARCH sh)
   add_definitions(-D__SUPPORT_VHEX_KERNEL)
+  set(FXLIBC_SHARED ON)
 endif()
 
 if(FXLIBC_TARGET STREQUAL vhex-x86)
   list(APPEND TARGET_FOLDERS vhex-generic x86-generic)
   set(FXLIBC_ARCH x86)
   add_definitions(-D__SUPPORT_VHEX_KERNEL)
+  set(FXLIBC_SHARED ON)
   # TODO: Maybe add -nostdinc (but that removes compiler-provided headers like
   # <stddef.h>), or use another compiler than the system one?
 endif()
@@ -246,16 +248,27 @@ if(casiowin-fx IN_LIST TARGET_FOLDERS)
     src/posix/unistd/target/casiowin-fx/close.S)
 endif()
 
-
-
 # TODO: All targets
 
 add_library(fxlibc ${SOURCES})
+
 target_include_directories(fxlibc PRIVATE include/)
 if(sh-generic IN_LIST TARGET_FOLDERS)
   target_include_directories(fxlibc PRIVATE "${FXSDK_COMPILER_INSTALL}/include/openlibm")
 endif()
 
+if(FXLIBC_SHARED)
+  target_compile_options(fxlibc PRIVATE -fPIC)
+
+  if("${FXLIBC_ARCH}" STREQUAL "sh")
+    # Original command: "ar qc <TARGET> <OBJECTS>; ranlib <TARGET>"
+    set(CMAKE_C_CREATE_STATIC_LIBRARY
+      "sh-elf-ld -shared <OBJECTS> -o <TARGET>")
+  else()
+    message(SEND_ERROR "TODO: Shared vhex on non-SuperH not available yet")
+  endif()
+endif()
+
 foreach(FOLDER IN LISTS TARGET_FOLDERS)
   target_include_directories(fxlibc PRIVATE include/target/${FOLDER}/)
 endforeach()