Relax FindGuile.cmake

* config/FindGuile.cmake: Do not require GUILE_ROOT_DIR since I'm not using
  it. Even though guile-config is available, guile-config --variable=prefix
  guile-3.0 fails somehow...

README.md

@@ -15,11 +15,18 @@ Except for the tests and for the pair of functions `ra->array` / `array->ra`, `n
 > cmake . && make test
 ```
 
+or manually
+
+```
+> $GUILE -L mod test/everything.scm
+> ...
+```
+
 The manual is at [lloda.github.io/guile-newra](https://lloda.github.io/guile-newra), and you can find some larger examples in `examples/`.
 
 To install the library, put `mod/newra` and `mod/newra.scm` somewhere in your Guile load path, and use it with `(import (newra))`.
 
-`newra` can use [`guile-ffi-blis`](https://github.com/lloda/guile-ffi-blis) for some functions (`ra-fill!` in the current version), which can provide a considerable speed up for operations with arrays of types `s32`, `u32`, `f32`, `s64`, `u64`, `f64`, `c32`, or `c64`. It can also be slower — there isn't a good heuristic yet. Run the benchmarks with
+`newra` can use [`guile-ffi-blis`](https://github.com/lloda/guile-ffi-blis) for some functions (`ra-fill!` in the current version), to provide a considerable speed up for operations with arrays of types `s32`, `u32`, `f32`, `s64`, `u64`, `f64`, `c32`, or `c64`. It can also be slower — there isn't a good heuristic yet. Run the benchmarks with
 
 ```
 > $GUILE -L mod bench/bench.scm

config/FindGuile.cmake

@@ -91,6 +91,8 @@ if (GUILE_CONFIG_EXECUTABLE)
 endif ()
 
 message ("* GUILE_EXECUTABLE: ${GUILE_EXECUTABLE}")
+message ("* GUILE_CONFIG_EXECUTABLE: ${GUILE_CONFIG_EXECUTABLE}")
+message ("* GUILE_ROOT: ${GUILE_ROOT}")
 message ("* GUILE_ROOT_DIR: ${GUILE_ROOT_DIR}")
 message ("* GUILE_INCLUDE_DIRS: ${GUILE_INCLUDE_DIRS}")
 message ("* GUILE_LIBRARIES: ${GUILE_LIBRARIES}")
@@ -99,7 +101,7 @@ message ("* GUILE_VERSION_STRING: ${GUILE_VERSION_STRING}")
 # handle REQUIRED and QUIET options
 include (FindPackageHandleStandardArgs)
 find_package_handle_standard_args (Guile
-  REQUIRED_VARS GUILE_EXECUTABLE GUILE_ROOT_DIR GUILE_INCLUDE_DIRS GUILE_LIBRARIES
+  REQUIRED_VARS GUILE_EXECUTABLE GUILE_INCLUDE_DIRS GUILE_LIBRARIES
   VERSION_VAR GUILE_VERSION_STRING)
 
 mark_as_advanced (GUILE_INCLUDE_DIR GUILE_LIBRARY)