Fix hyperlinks in documentation

Author: mpilgrem

doc/environment_variables.md

@@ -74,7 +74,7 @@ Related command: all commands that make use of Stack's global YAML configuration
 file (`config.yaml`).
 
 Overridden by: Stack's global
-[`--stack-root`](global_flags.md#stack-root-option) option.
+[`--stack-root`](global_flags.md#-stack-root-option) option.
 
 The environment variable `STACK_ROOT` can be used to specify the Stack root
 directory.
@@ -85,7 +85,7 @@ Related command: all commands that make use of Stack's work directories.
 
 Overridden by: Stack's [`work-dir`](yaml_configuration.md#work-dir) non-project
 specific configuration option, or global
-[`--work-dir`](global_flags.md#work-dir-option) option.
+[`--work-dir`](global_flags.md#-work-dir-option) option.
 
 The environment variable `STACK_WORK` can be used to specify the path of Stack's
 work directory, within a local project or package directory, and override
@@ -100,7 +100,7 @@ YAML configuration file (`config.yaml`).
 
 Overridden by: the use of Stack's `STACK_ROOT` environment variable, or the use
 of Stack's global
-[`--stack-root`](global_flags.md#stack-root-option) option.
+[`--stack-root`](global_flags.md#-stack-root-option) option.
 
 On Unix-like operating systems and Windows, Stack can be configured to follow
 the XDG Base Directory Specification if the environment variable `STACK_XDG` is
@@ -112,7 +112,7 @@ Related command: all commands that make use of Stack's project-level YAML
 configuration file.
 
 Overridden by: Stack's global
-[`--stack-yaml`](global_flags.md#stack-yaml-option) option.
+[`--stack-yaml`](global_flags.md#-stack-yaml-option) option.
 
 The environment variable `STACK_YAML` can be used to specify Stack's
 project-level YAML configuration file.

doc/yaml_configuration.md

@@ -1566,7 +1566,7 @@ with-hpack: /usr/local/bin/hpack
 Default: `.stack-work`
 
 Command line equivalent (takes precedence):
-[`--work-dir`](global_flags.md#work-dir-option) option
+[`--work-dir`](global_flags.md#-work-dir-option) option
 
 Environment variable alternative (lowest precedence):
 [`STACK_WORK`](environment_variables.md#stack_work)