deps: pass LDFLAGS+=-static (#11138)

This is required when `build_old_libs=no` is used in `libtool`.

Fixes https://github.com/neovim/neovim/issues/11198

third-party/cmake/BuildLibtermkey.cmake

@@ -48,6 +48,7 @@ ExternalProject_Add(libtermkey
                               PREFIX=${DEPS_INSTALL_DIR}
                               PKG_CONFIG_PATH=${DEPS_LIB_DIR}/pkgconfig
                               CFLAGS=-fPIC
+                              LDFLAGS+=-static
                               ${DEFAULT_MAKE_CFLAGS}
                               install)
 endif()

third-party/cmake/BuildLibvterm.cmake

@@ -58,6 +58,7 @@ else()
   set(LIBVTERM_INSTALL_COMMAND ${MAKE_PRG} CC=${DEPS_C_COMPILER}
                                            PREFIX=${DEPS_INSTALL_DIR}
                                            CFLAGS=-fPIC
+                                           LDFLAGS+=-static
                                            ${DEFAULT_MAKE_CFLAGS}
                                            install)
 endif()

third-party/cmake/BuildUnibilium.cmake

@@ -40,6 +40,7 @@ else()
     BUILD_COMMAND ${MAKE_PRG} CC=${DEPS_C_COMPILER}
                               PREFIX=${DEPS_INSTALL_DIR}
                               CFLAGS=-fPIC
+                              LDFLAGS+=-static
     INSTALL_COMMAND ${MAKE_PRG} PREFIX=${DEPS_INSTALL_DIR} install)
 endif()