bench: fix Makefile and move to subfolder

---
type: pre_commit_static_analysis_report
description: Results of running static analysis checks when committing changes.
report:
  - task: lint_filenames
    status: passed
  - task: lint_editorconfig
    status: passed
  - task: lint_markdown
    status: na
  - task: lint_package_json
    status: na
  - task: lint_repl_help
    status: na
  - task: lint_javascript_src
    status: na
  - task: lint_javascript_cli
    status: na
  - task: lint_javascript_examples
    status: na
  - task: lint_javascript_tests
    status: na
  - task: lint_javascript_benchmarks
    status: na
  - task: lint_python
    status: na
  - task: lint_r
    status: na
  - task: lint_c_src
    status: na
  - task: lint_c_examples
    status: na
  - task: lint_c_benchmarks
    status: passed
  - task: lint_c_tests_fixtures
    status: na
  - task: lint_shell
    status: na
  - task: lint_typescript_declarations
    status: na
  - task: lint_typescript_tests
    status: na
  - task: lint_license_headers
    status: passed
---

Author: kgryte

lib/node_modules/@stdlib/blas/ext/base/dsortins/benchmark/c/Makefile renamed to lib/node_modules/@stdlib/blas/ext/base/dsortins/benchmark/c/unsorted-random/Makefile

@@ -82,7 +82,7 @@ LIBRARIES ?=
 LIBPATH ?=
 
 # List of C targets:
-c_targets := example.out
+c_targets := benchmark.length.out
 
 
 # RULES #
@@ -124,7 +124,7 @@ $(c_targets): %.out: %.c
 	$(QUIET) $(CC) $(CFLAGS) $(fPIC) $(INCLUDE) -o $@ $(SOURCE_FILES) $< $(LIBPATH) -lm $(LIBRARIES)
 
 #/
-# Runs compiled examples.
+# Runs compiled benchmarks.
 #
 # @example
 # make run