Remove jerry-libc (#2332)

Rationale:
- There is no port under targets/ that would use it. All of them
  turn it off when building.
- That's no surprise, as jerry-libc supports no barebone MCUs but
  posix targets with syscalls only. Actually, that's Linux only,
  because macOS builds have turned off the use of jerry-libc a
  while ago.
- And there is no point in maintaining a highly restricted set of
  libc functions: as soon as someone wants to use JerryScript in a
  scenario that needs more functions than jerry-main, they have to
  choose a different libc (most problably the compiler's default
  one).

I think that we should not keep supporting an otherwise unused
library for the purposes of jerry-main on arm/x86/x64-linux  only.

JerryScript-DCO-1.0-Signed-off-by: Akos Kiss akiss@inf.u-szeged.hu

tools/check-cppcheck.sh

@@ -25,12 +25,11 @@ fi
 JERRY_CORE_DIRS=`find jerry-core -type d`
 JERRY_EXT_DIRS=`find jerry-ext -type d`
 JERRY_PORT_DIRS=`find jerry-port -type d`
-JERRY_LIBC_DIRS=`find jerry-libc -type d`
 JERRY_LIBM_DIRS=`find jerry-libm -type d`
 
 
 INCLUDE_DIRS=()
-for DIR in $JERRY_CORE_DIRS $JERRY_EXT_DIRS $JERRY_PORT_DIRS $JERRY_LIBC_DIRS $JERRY_LIBM_DIRS
+for DIR in $JERRY_CORE_DIRS $JERRY_EXT_DIRS $JERRY_PORT_DIRS $JERRY_LIBM_DIRS
 do
   INCLUDE_DIRS=("${INCLUDE_DIRS[@]}" "-I$DIR")
 done
@@ -44,4 +43,4 @@ cppcheck -j$CPPCHECK_JOBS --force \
   --exitcode-suppressions=tools/cppcheck/suppressions-list \
   --suppressions-list=tools/cppcheck/suppressions-list \
   "${INCLUDE_DIRS[@]}" \
-  jerry-core jerry-ext jerry-port jerry-libc jerry-libm jerry-main tests/unit-*
+  jerry-core jerry-ext jerry-port jerry-libm jerry-main tests/unit-*