fpm_environment: lower windows check precedence in get_os_type function (#802)

Author: sloorush

src/fpm_environment.f90

@@ -51,15 +51,6 @@ integer function get_os_type() result(r)
         first_run = .false.
         r = OS_UNKNOWN
 
-        ! Check environment variable `OS`.
-        call get_environment_variable('OS', val, length, rc)
-
-        if (rc == 0 .and. length > 0 .and. index(val, 'Windows_NT') > 0) then
-            r = OS_WINDOWS
-            ret = r
-            return
-        end if
-
         ! Check environment variable `OSTYPE`.
         call get_environment_variable('OSTYPE', val, length, rc)
 
@@ -114,6 +105,15 @@ integer function get_os_type() result(r)
             end if
         end if
 
+        ! Check environment variable `OS`.
+        call get_environment_variable('OS', val, length, rc)
+
+        if (rc == 0 .and. length > 0 .and. index(val, 'Windows_NT') > 0) then
+            r = OS_WINDOWS
+            ret = r
+            return
+        end if
+
         ! Linux
         inquire (file='/etc/os-release', exist=file_exists)