test: improve test script to allow easily adding new runs

test.sh previously had each of its runs hard-coded; this patch changes
the script to loop over an array of cargo flags instead. This allows new
flags to be added to the array to easily add new runs to the test
script.

test.sh

@@ -2,17 +2,15 @@
 set -e
 set -o pipefail
 
-# no_std and no alloc
-cargo +nightly miri test --no-default-features --features serde
+TEST_RUNS=(
+    '--no-default-features --features serde'
+    '--no-default-features --features alloc,serde'
+    '--features serde'
+    '--target sparc-unknown-linux-gnu --features serde'
+    '--target mips64-unknown-linux-gnuabi64 --features serde'
+)
 
-# no_std with alloc
-cargo +nightly miri test --no-default-features --features alloc,serde
-
-# std
-cargo +nightly miri test --features serde
-
-# 32-bit target
-cargo +nightly miri test --target sparc-unknown-linux-gnu --features serde
-
-# Big-endian target
-cargo +nightly miri test --target mips64-unknown-linux-gnuabi64 --features serde
+for FLAGS in "${TEST_RUNS[@]}"
+do
+    cargo +nightly miri test $FLAGS
+done