Fixing rogue tabs

I know this is petty, but the CONTRIBUTING.md is pretty clear on this: "whitespaces, no tabs".

First of all, commit 5f04b34b introduced inconsistent tabbing (vim style suggests 4 space tabs). The patch below fixes this (assuming tab characters survive markdown&web):

diff --git a/ghcup b/ghcup
index cc9c3f4..cd5f7e3 100755
--- a/ghcup
+++ b/ghcup
@@ -1102,9 +1102,9 @@ get_distro_alias() {
         "Linux Mint"|"LinuxMint")
             distro_alias=mint
             ;;
-	"Amazon Linux AMI")
-	    distro_alias=amazonlinux
-	    ;;
+        "Amazon Linux AMI")
+            distro_alias=amazonlinux
+            ;;
         "AIX")
             distro_alias=aix
             ;;

Second, more contentious, and perhaps a bit gratuitous, the "here file" introduced by commit b2b020ef also breaks the "no tabs" rule, and is fixed by the patch below (sorry, it does come out a bit ugly):

diff --git a/ghcup b/ghcup
index cc9c3f4..c0af266 100755
--- a/ghcup
+++ b/ghcup
@@ -1752,14 +1752,14 @@ compile_ghc() {
         if [ -n "${build_config}" ] ; then
             edo cat "${build_config}" > mk/build.mk
         else
-                       cat <<-EOF > mk/build.mk || die
-                               V=0
-                               BUILD_MAN = NO
-                               BUILD_SPHINX_HTML = NO
-                               BUILD_SPHINX_PDF = NO
-                               HADDOCK_DOCS = YES
-                               GhcWithLlvmCodeGen = YES
-                               EOF
+            cat <<EOF > mk/build.mk || die
+V=0
+BUILD_MAN = NO
+BUILD_SPHINX_HTML = NO
+BUILD_SPHINX_PDF = NO
+HADDOCK_DOCS = YES
+GhcWithLlvmCodeGen = YES
+EOF
         fi