Dependency checks for cmake (req. by emsdk) and libtool (req. by libffi) (#2423)

Earlier errors about these should make building smoother for new contributors.

docs/project/changelog.md

@@ -26,6 +26,8 @@ substitutions:
   `pyodide.runPython(code, { globals : some_dict})`;
   {pr}`2391`
 
+- {{ Bugfix }} The build will error out earlier if `cmake` or `libtool` are not installed.
+
 ### Packages
 
 - {{ Enhancement }} Pillow now supports WEBP image format {pr}`2407`.

tools/dependency-check.sh

@@ -36,6 +36,14 @@ check_shasum() {
   check_binary_present "shasum"
 }
 
+check_cmake() {
+  check_binary_present "cmake"
+}
+
+check_libtool() {
+  check_binary_present "libtool"
+}
+
 check_fortran_dependencies() {
   check_binary_present "gfortran"
   check_binary_present "f2c"