depends: Drop trailing slash from CMAKE_INSTALL_LIBDIR

1. The trailing slash is redundant.
2. It causes warnings when using CMake >=3.31:
```
CMake Warning (dev) at CMakeLists.txt:596 (install):
  Policy CMP0177 is not set: install() DESTINATION paths are normalized.  Run
  "cmake --help-policy CMP0177" for policy details.  Use the cmake_policy
  command to set the policy and suppress this warning.
This warning is for project developers.  Use -Wno-dev to suppress it.

```

depends/funcs.mk

@@ -222,7 +222,7 @@ $(1)_cmake=env CC="$$($(1)_cc)" \
                -DCMAKE_AR=`which $$($(1)_ar)` \
                -DCMAKE_NM=`which $$($(1)_nm)` \
                -DCMAKE_RANLIB=`which $$($(1)_ranlib)` \
-               -DCMAKE_INSTALL_LIBDIR=lib/ \
+               -DCMAKE_INSTALL_LIBDIR=lib \
                -DCMAKE_POSITION_INDEPENDENT_CODE=ON \
                -DCMAKE_VERBOSE_MAKEFILE:BOOL=$(V) \
                -DCMAKE_EXPORT_NO_PACKAGE_REGISTRY:BOOL=TRUE \