[frogr] Update INSTALL not to mention the Build API

[Mario Sanchez Prada <msanchez src gnome org>]

commit 6adf26cbf96658f5823eae47894fb89481f18f6e
Author: Mario Sanchez Prada <msanchez gnome org>
Date:   Thu Jan 9 13:22:47 2020 +0100

    Update INSTALL not to mention the Build API

 INSTALL | 12 ++----------
 1 file changed, 2 insertions(+), 10 deletions(-)
---
diff --git a/INSTALL b/INSTALL
index 77dab56..9b0d5c4 100644
--- a/INSTALL
+++ b/INSTALL
@@ -1,17 +1,9 @@
 Compiling from source code
 ==========================
 
-To compile and try the application you need to have meson and ninja
-installed, but you can still use the usual commands defined by
-the build API (see https://github.com/cgwalters/build-api):
+To compile and try the application you need to have meson and ninja:
 
- $ ./configure
- $ make
- $ make install
-
-To use meson and ninja, instead of using the wrapper configure script:
-
- $ meson . BUILD
+ $ meson --prefix /local/install/path . BUILD
  $ ninja -C BUILD
  $ ninja -C BUILD install