Limited byte-level tests to native testing due to time

Byte-level writes are expensive and not suggested (caches >= 4 bytes
make much more sense), however there are many corner cases with
byte-level writes that can be easy to miss (power-loss leaving single
bytes written to disk).

Unfortunately, byte-level writes mixed with power-loss testing, the
Travis infrastructure, and Arm Thumb instruction set simulation
exceeds the 50-minute budget Travis allocates for jobs.

For now I'm disabling the byte-level tests under Qemu, with the hope that
performance improvements in littlefs will let us turn these tests back
on in the future.

.travis.yml

@@ -115,7 +115,7 @@ jobs:
     env:
       - NAME=littlefs-arm
       - CC="arm-linux-gnueabi-gcc --static -mthumb"
-      - TFLAGS="$TFLAGS -e qemu-arm"
+      - TFLAGS="$TFLAGS --exec=qemu-arm"
     install:
       - *install-common
       - sudo apt-get install
@@ -131,7 +131,9 @@ jobs:
   - {<<: *arm, script: [*test-nand,             *report-size]}
   - {<<: *arm, script: [*test-no-intrinsics,    *report-size]}
   - {<<: *arm, script: [*test-no-inline,        *report-size]}
-  - {<<: *arm, script: [*test-byte-writes,      *report-size]}
+  # it just takes way to long to run byte-level writes in qemu,
+  # note this is still tested in the native tests
+  #- {<<: *arm, script: [*test-byte-writes,      *report-size]}
   - {<<: *arm, script: [*test-block-cycles,     *report-size]}
   - {<<: *arm, script: [*test-odd-block-count,  *report-size]}
   - {<<: *arm, script: [*test-odd-block-size,   *report-size]}
@@ -142,7 +144,7 @@ jobs:
     env:
       - NAME=littlefs-mips
       - CC="mips-linux-gnu-gcc --static"
-      - TFLAGS="$TFLAGS -e qemu-mips"
+      - TFLAGS="$TFLAGS --exec=qemu-mips"
     install:
       - *install-common
       - sudo apt-get install
@@ -158,7 +160,9 @@ jobs:
   - {<<: *mips, script: [*test-nand,             *report-size]}
   - {<<: *mips, script: [*test-no-intrinsics,    *report-size]}
   - {<<: *mips, script: [*test-no-inline,        *report-size]}
-  - {<<: *mips, script: [*test-byte-writes,      *report-size]}
+  # it just takes way to long to run byte-level writes in qemu,
+  # note this is still tested in the native tests
+  #- {<<: *mips, script: [*test-byte-writes,      *report-size]}
   - {<<: *mips, script: [*test-block-cycles,     *report-size]}
   - {<<: *mips, script: [*test-odd-block-count,  *report-size]}
   - {<<: *mips, script: [*test-odd-block-size,   *report-size]}
@@ -169,7 +173,7 @@ jobs:
     env:
       - NAME=littlefs-powerpc
       - CC="powerpc-linux-gnu-gcc --static"
-      - TFLAGS="$TFLAGS -e qemu-ppc"
+      - TFLAGS="$TFLAGS --exec=qemu-ppc"
     install:
       - *install-common
       - sudo apt-get install
@@ -185,7 +189,9 @@ jobs:
   - {<<: *powerpc, script: [*test-nand,             *report-size]}
   - {<<: *powerpc, script: [*test-no-intrinsics,    *report-size]}
   - {<<: *powerpc, script: [*test-no-inline,        *report-size]}
-  - {<<: *powerpc, script: [*test-byte-writes,      *report-size]}
+  # it just takes way to long to run byte-level writes in qemu,
+  # note this is still tested in the native tests
+  #- {<<: *powerpc, script: [*test-byte-writes,      *report-size]}
   - {<<: *powerpc, script: [*test-block-cycles,     *report-size]}
   - {<<: *powerpc, script: [*test-odd-block-count,  *report-size]}
   - {<<: *powerpc, script: [*test-odd-block-size,   *report-size]}

tests/test_dirs.toml

@@ -157,7 +157,6 @@ code = '''
 [[case]] # reentrant many directory creation/rename/removal
 define.N = [5, 11]
 reentrant = true
-if = 'LFS_CACHE_SIZE >= 4' # these just take too long with byte-level writes
 code = '''
     err = lfs_mount(&lfs, &cfg);
     if (err) {
@@ -384,7 +383,6 @@ code = '''
 [[case]] # reentrant file creation/rename/removal
 define.N = [5, 25]
 reentrant = true
-if = 'LFS_CACHE_SIZE >= 4' # these just take too long with byte-level writes
 code = '''
     err = lfs_mount(&lfs, &cfg);
     if (err) {